#pragma region Macros #pragma comment(linker, "/stack:200000000") // #pragma GCC optimize("unroll-loops") // #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,fma,abm,mmx,avx,avx2,tune=native") // #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,fma,abm,mmx,avx,avx2") // #pragma GCC target("avx2") #pragma GCC optimize("Ofast") #include #define ll long long using ld = long double; #define rep2(i, a, b) for(ll i = (a); i <= (b); i++) #define rep3(i, a, b) for(ll i = (a); i >= (b); --i) #define rep(i, n) for(ll i = 0; i < n; ++i) #define each(i, a) for(auto &i : a) #define pii pair #define pll pair #define pb push_back #define eb emplace_back #define vi vector #define vll vector #define vpi vector #define vpll vector #define overload2(_1, _2, name, ...) name #define vec(type, name, ...) vector name(__VA_ARGS__) #define VEC(type, name, size) \ vector name(size); \ IN(name) #define VEC2(type, name1, name2, size) \ vector name1(size), name2(size); \ for(int i = 0; i < size; i++) IN(name1[i], name2[i]) #define VEC3(type, name1, name2, name3, size) \ vector name1(size), name2(size), name3(size); \ for(int i = 0; i < size; i++) IN(name1[i], name2[i], name3[i]) #define vv(type, name, h, ...) vector> name(h, vector(__VA_ARGS__)) #define VV(type, name, h, w) \ vector> name(h, vector(w)); \ IN(name) #define vvv(type, name, h, w, ...) vector>> name(h, vector>(w, vector(__VA_ARGS__))) #define vvvv(type, name, a, b, c, ...) \ vector>>> name(a, vector>>(b, vector>(c, vector(__VA_ARGS__)))) #define mt make_tuple #define fi first #define se second #define all(c) begin(c), end(c) #define rall(c) rbegin(c), rend(c) #define SORT(v) sort(all(v)) #define REV(v) reverse(all(v)) template T SUM(const S &v) { return accumulate(all(v), T(0)); } #define MIN(v) *min_element(all(v)) #define MAX(v) *max_element(all(v)) #define lb(c, x) distance((c).begin(), lower_bound(all(c), (x))) #define ub(c, x) distance((c).begin(), upper_bound(all(c), (x))) using namespace std; constexpr pii dx4[4] = {pii{1, 0}, pii{0, 1}, pii{-1, 0}, pii{0, -1}}; constexpr pii dx8[8] = {{1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}, {-1, -1}, {0, -1}, {1, -1}}; const string YESNO[2] = {"NO", "YES"}; const string YesNo[2] = {"No", "Yes"}; const string yesno[2] = {"no", "yes"}; void YES(bool t = 1) { cout << YESNO[t] << endl; } void NO(bool t = 1) { YES(!t); } void Yes(bool t = 1) { cout << YesNo[t] << endl; } void No(bool t = 1) { Yes(!t); } void yes(bool t = 1) { cout << yesno[t] << endl; } void no(bool t = 1) { yes(!t); } template using vc = vector; template using vvc = vector>; template using vvvc = vector>; template using vvvvc = vector>; template using pq = priority_queue; template using pqg = priority_queue, greater>; #define si(c) (int)(c).size() #define INT(...) \ int __VA_ARGS__; \ IN(__VA_ARGS__) #define LL(...) \ ll __VA_ARGS__; \ IN(__VA_ARGS__) #define STR(...) \ string __VA_ARGS__; \ IN(__VA_ARGS__) #define CHR(...) \ char __VA_ARGS__; \ IN(__VA_ARGS__) #define DBL(...) \ double __VA_ARGS__; \ IN(__VA_ARGS__) int scan() { return getchar(); } void scan(int &a) { cin >> a; } void scan(long long &a) { cin >> a; } void scan(char &a) { cin >> a; } void scan(double &a) { cin >> a; } void scan(string &a) { cin >> a; } template void scan(pair &p) { scan(p.first), scan(p.second); } template void scan(vector &); template void scan(vector &a) { for(auto &i : a) scan(i); } template void scan(T &a) { cin >> a; } void IN() {} template void IN(Head &head, Tail &...tail) { scan(head); IN(tail...); } template inline bool chmax(T &a, const S &b) { return (a < b ? a = b, 1 : 0); } template inline bool chmin(T &a, const S &b) { return (a > b ? a = b, 1 : 0); } vi iota(int n) { vi a(n); iota(all(a), 0); return a; } template vi iota(vector &a, bool greater = false) { vi res(a.size()); iota(all(res), 0); sort(all(res), [&](int i, int j) { if(greater) return a[i] > a[j]; return a[i] < a[j]; }); return res; } #define UNIQUE(x) sort(all(x)), x.erase(unique(all(x)), x.end()) template T ceil(T x, T y) { assert(y >= 1); return (x > 0 ? (x + y - 1) / y : x / y); } template T floor(T x, T y) { assert(y >= 1); return (x > 0 ? x / y : (x + y - 1) / y); } template T POW(T x, int n) { T res = 1; for(; n; n >>= 1, x *= x) if(n & 1) res *= x; return res; } template T POW(T x, S n, const ll &mod) { T res = 1; for(; n; n >>= 1, x = x * x % mod) if(n & 1) res = res * x % mod; return res; } vector factor(ll x) { vector ans; for(ll i = 2; i * i <= x; i++) if(x % i == 0) { ans.push_back({i, 1}); while((x /= i) % i == 0) ans.back().second++; } if(x != 1) ans.push_back({x, 1}); return ans; } template vector divisor(T x) { vector ans; for(T i = 1; i * i <= x; i++) if(x % i == 0) { ans.pb(i); if(i * i != x) ans.pb(x / i); } return ans; } template void zip(vector &x) { vector y = x; UNIQUE(y); for(int i = 0; i < x.size(); ++i) { x[i] = lb(y, x[i]); } } template void fold_in(vector &v) {} template void fold_in(vector &v, Head &&a, Tail &&...tail) { for(auto e : a) v.emplace_back(e); fold_in(v, tail...); } template void renumber(vector &v) {} template void renumber(vector &v, Head &&a, Tail &&...tail) { for(auto &&e : a) e = lb(v, e); renumber(v, tail...); } template vector zip(vector &head, Args &&...args) { vector v; fold_in(v, head, args...); sort(all(v)), v.erase(unique(all(v)), v.end()); renumber(v, head, args...); return v; } // x in [l, r) template bool inc(const T &x, const S &l, const S &r) { return l <= x and x < r; } // (a, b) in [lx, rx) * [ly, ry) template bool inc(const pair &x, const S &lx, const S &ly, const S &rx, const S &ry) { return inc(x.fi, lx, rx) && inc(x.se, ly, ry); } constexpr ll ten(int n) { return n == 0 ? 1 : ten(n - 1) * 10; } // bit 演算系 ll pow2(int i) { return 1LL << i; } int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); } int topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); } int lowbit(signed a) { return a == 0 ? 32 : __builtin_ctz(a); } int lowbit(ll a) { return a == 0 ? 64 : __builtin_ctzll(a); } // int allbit(int n) { return (1 << n) - 1; } ll allbit(ll n) { return (1LL << n) - 1; } int popcount(signed t) { return __builtin_popcount(t); } int popcount(ll t) { return __builtin_popcountll(t); } bool ispow2(int i) { return i && (i & -i) == i; } ll rnd(ll l, ll r) { //[l, r) #ifdef _LOCAL static mt19937_64 gen; #else static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count()); #endif return uniform_int_distribution(l, r - 1)(gen); } ll rnd(ll n) { return rnd(0, n); } template void random_shuffle(vc &a) { rep(i, si(a)) swap(a[i], a[rnd(0, i + 1)]); } int in() { int x; cin >> x; return x; } ll lin() { unsigned long long x; cin >> x; return x; } template pair operator-(const pair &x, const pair &y) { return pair(x.fi - y.fi, x.se - y.se); } template pair operator+(const pair &x, const pair &y) { return pair(x.fi + y.fi, x.se + y.se); } template pair operator&(const pair &l, const pair &r) { return pair(max(l.fi, r.fi), min(l.se, r.se)); } template pair operator+=(pair &l, const pair &r) { return l = l + r; } template pair operator-=(pair &l, const pair &r) { return l = l - r; } template bool intersect(const pair &l, const pair &r) { return (l.se < r.se ? r.fi < l.se : l.fi < r.se); } template ll operator*(const pair &x, const pair &y) { return (ll)x.fi * y.fi + (ll)x.se * y.se; } template struct edge { int from, to; T cost; int id; edge(int to, T cost) : from(-1), to(to), cost(cost) {} edge(int from, int to, T cost) : from(from), to(to), cost(cost) {} edge(int from, int to, T cost, int id) : from(from), to(to), cost(cost), id(id) {} constexpr bool operator<(const edge &rhs) const noexcept { return cost < rhs.cost; } edge &operator=(const int &x) { to = x; return *this; } operator int() const { return to; } }; template using Edges = vector>; using Tree = vector>; using Graph = vector>; template using Wgraph = vector>>; Graph getG(int n, int m = -1, bool directed = false, int margin = 1) { Tree res(n); if(m == -1) m = n - 1; while(m--) { int a, b; cin >> a >> b; a -= margin, b -= margin; res[a].emplace_back(b); if(!directed) res[b].emplace_back(a); } return res; } Graph getTreeFromPar(int n, int margin = 1) { Graph res(n); for(int i = 1; i < n; i++) { int a; cin >> a; res[a - margin].emplace_back(i); } return res; } template Wgraph getWg(int n, int m = -1, bool directed = false, int margin = 1) { Wgraph res(n); if(m == -1) m = n - 1; while(m--) { int a, b; T c; cin >> a >> b >> c; a -= margin, b -= margin; res[a].emplace_back(b, c); if(!directed) res[b].emplace_back(a, c); } return res; } void add(Graph &G, int x, int y) { G[x].eb(y), G[y].eb(x); } template void add(Wgraph &G, int x, int y, T c) { G[x].eb(y, c), G[y].eb(x, c); } #define i128 __int128_t #define ull unsigned long long int #define TEST \ INT(testcases); \ while(testcases--) template ostream &operator<<(ostream &os, const vector &v) { for(auto it = begin(v); it != end(v); ++it) { if(it == begin(v)) os << *it; else os << " " << *it; } return os; } template ostream &operator<<(ostream &os, const pair &p) { os << p.first << " " << p.second; return os; } template string to_string(pair p) { return "(" + to_string(p.first) + "," + to_string(p.second) + ")"; } string to_string(string s) { return "\"" + s + "\""; } string to_string(char c) { return string(1, c); } template string to_string(vector s) { string res = "{"; for(auto it = s.begin(); it != s.end(); it++) res += to_string(*it) + (next(it) == s.end() ? "" : ", "); return res + "}"; } template string to_string(set s) { string res = "{"; for(auto it = s.begin(); it != s.end(); it++) res += to_string(*it), res += (next(it) == end(s) ? "" : ", "); return res + "}"; } #define endl '\n' #ifdef _LOCAL void dump() { cerr << endl; } template void dump(Head head, Tail... tail) { cerr << to_string(head) << " "; dump(tail...); } #undef endl #define debug(x) \ cout << #x << ": "; \ dump(x) #else void dump() {} template void dump(Head head, Tail... tail) {} #define debug(x) #endif template void print(const T &a) { cout << a; } void OUT() { cout << endl; } template void OUT(const Head &head, const Tail &...tail) { print(head); if(sizeof...(tail)) cout << ' '; OUT(tail...); } template static constexpr T inf = numeric_limits::max() / 2; struct Setup_io { Setup_io() { ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0); cout << fixed << setprecision(15); } } setup_io; #define drop(s) cout << #s << endl, exit(0) template struct ndFORarray { std::array v; ndFORarray(std::array v_) : v(v_) {} struct ndFORitr { const std::array &v; std::array tmp; bool is_end; ndFORitr(const std::array &v_) : v(v_), tmp(), is_end(false) {} bool operator!=(const ndFORitr &) const { return !is_end; } void operator++() { int pos = N - 1; while(pos != -1) { tmp[pos] += 1; if(tmp[pos] == v[pos]) { tmp[pos] = 0; pos -= 1; } else { break; } } if(pos == -1) { is_end = true; } } const std::array &operator*() const { return tmp; } }; ndFORitr begin() const { return ndFORitr(v); } ndFORitr end() const { return ndFORitr(v); } }; struct ndFORvector { std::vector v; ndFORvector(std::vector v_) : v(v_) {} struct ndFORitr { const std::vector &v; std::vector tmp; bool is_end; ndFORitr(const std::vector &v_) : v(v_), tmp(v.size(), 0), is_end(false) {} bool operator!=(const ndFORitr &) const { return !is_end; } void operator++() { int pos = v.size() - 1; while(pos != -1) { tmp[pos] += 1; if(tmp[pos] == v[pos]) { tmp[pos] = 0; pos -= 1; } else { break; } } if(pos == -1) { is_end = true; } } const std::vector &operator*() const { return tmp; } }; ndFORitr begin() const { return ndFORitr(v); } ndFORitr end() const { return ndFORitr(v); } }; auto ndFOR(std::vector v) { return ndFORvector(v); } template auto ndFOR(Ts... v) { return ndFORarray>::value>({v...}); } template struct REC { F f; REC(F &&f_) : f(std::forward(f_)) {} template auto operator()(Args &&...args) const { return f(*this, std::forward(args)...); } }; template vector> runLength(const vector &v) { vector> res; for(auto &e : v) { if(res.empty() or res.back().fi != e) res.eb(e, 1); else res.back().se++; } return res; } vector> runLength(const string &v) { vector> res; for(auto &e : v) { if(res.empty() or res.back().fi != e) res.eb(e, 1); else res.back().se++; } return res; } template struct Imos { int n; vector a; Imos(int _n) : n(_n), a(_n + 1) {} void add(int l, int r, T val = 1) { if(l >= r) return; l = clamp(l, 0, n); r = clamp(r, 0, n + 1); a[l] += val; if(r <= n) a[r] -= val; } void build() { for(int i = 0; i < n; i++) a[i + 1] += a[i]; } const T &operator[](int k) { return a[k]; } }; template struct RUI { vector a; RUI(const vector &v) : a(v.size() + 1) { for(int i = 0; i < v.size(); i++) a[i + 1] = a[i] + v[i]; } T get(int l, int r) { return a[r] - a[l]; } }; template T bin_search(T ok, T ng, const F &f) { while(abs(ok - ng) > 1) { T mid = ok + ng >> 1; (f(mid) ? ok : ng) = mid; } return ok; } #pragma endregion namespace modular { constexpr ll MOD = 1000000007; const int MAXN = 11000000; template class modint; #define mint modint #define vmint vector vector Inv; mint inv(int x); template class modint { public: static constexpr int mod() { return Modulus; } ll a; constexpr modint(const ll x = 0) noexcept : a(((x % Modulus) + Modulus) % Modulus) {} constexpr ll &value() noexcept { return a; } constexpr const ll &value() const noexcept { return a; } constexpr modint operator-() const noexcept { return modint() - *this; } constexpr modint operator+() const noexcept { return *this; } constexpr modint &operator++() noexcept { if(++a == MOD) a = 0; return *this; } constexpr modint &operator--() noexcept { if(!a) a = MOD; a--; return *this; } constexpr modint operator++(int) { modint res = *this; ++*this; return res; } constexpr modint operator--(int) { mint res = *this; --*this; return res; } constexpr modint &operator+=(const modint rhs) noexcept { a += rhs.a; if(a >= Modulus) { a -= Modulus; } return *this; } constexpr modint &operator-=(const modint rhs) noexcept { if(a < rhs.a) { a += Modulus; } a -= rhs.a; return *this; } constexpr modint &operator*=(const modint rhs) noexcept { a = a * rhs.a % Modulus; return *this; } constexpr modint &operator/=(const modint rhs) noexcept { a = a * (modular::inv(rhs.a)).a % Modulus; return *this; } constexpr modint pow(long long n) const noexcept { if(n < 0) { n %= Modulus - 1; n = (Modulus - 1) + n; } modint x = *this, r = 1; while(n) { if(n & 1) r *= x; x *= x; n >>= 1; } return r; } constexpr modint inv() const noexcept { return pow(Modulus - 2); } constexpr friend modint operator+(const modint &lhs, const modint &rhs) { return modint(lhs) += modint(rhs); } constexpr friend modint operator-(const modint &lhs, const modint &rhs) { return modint(lhs) -= modint(rhs); } constexpr friend modint operator*(const modint &lhs, const modint &rhs) { return modint(lhs) *= modint(rhs); } constexpr friend modint operator/(const modint &lhs, const modint &rhs) { return modint(lhs) /= modint(rhs); } constexpr friend modint operator==(const modint &lhs, const modint &rhs) { return lhs.a == rhs.a; } constexpr friend modint operator!=(const modint &lhs, const modint &rhs) { return lhs.a != rhs.a; } // constexpr friend modint operator^=(const modint &lhs, const modint &rhs) { return modint(lhs) ^= modint(rhs); } }; vmint Fact{1, 1}, Ifact{1, 1}; mint inv(int n) { if(n > MAXN) return (mint(n)).pow(MOD - 2); if(Inv.empty()) Inv.emplace_back(0), Inv.emplace_back(1); if(Inv.size() > n) return Inv[n]; else { for(int i = Inv.size(); i <= n; ++i) { auto [y, x] = div(int(MOD), i); Inv.emplace_back(Inv[x] * (-y)); } return Inv[n]; } } mint fact(int n) { if(Fact.size() > n) return Fact[n]; else for(int i = Fact.size(); i <= n; ++i) Fact.emplace_back(Fact[i - 1] * i); return Fact[n]; } mint ifact(int n) { if(Ifact.size() > n) return Ifact[n]; else for(int i = Ifact.size(); i <= n; ++i) Ifact.emplace_back(Ifact[i - 1] * inv(i)); return Ifact[n]; } mint modpow(ll a, ll n) { return mint(a).pow(n); } mint inv(mint a) { return inv(a.a); } mint ifact(mint a) { return ifact(a.a); } mint fact(mint a) { return fact(a.a); } mint modpow(mint a, ll n) { return modpow(a.a, n); } mint C(int a, int b) { if(a < 0 || b < 0) return 0; if(a < b) return 0; if(a > MAXN) { mint res = 1; rep(i, b) res *= a - i, res /= i + 1; return res; } return fact(a) * ifact(b) * ifact(a - b); } mint P(int a, int b) { if(a < 0 || b < 0) return 0; if(a < b) return 0; if(a > MAXN) { mint res = 1; rep(i, b) res *= a - i; return res; } return fact(a) * ifact(a - b); } ostream &operator<<(ostream &os, mint a) { os << a.a; return os; } istream &operator>>(istream &is, mint &a) { ll x; is >> x; a = x; return is; } struct modinfo { int mod, root; }; constexpr modinfo base0{1045430273, 3}; constexpr modinfo base1{1051721729, 6}; constexpr modinfo base2{1053818881, 7}; using mint0 = modint; using mint1 = modint; using mint2 = modint; using Poly = vmint; template void FMT(vector> &f, bool inv = false) { using V = vector>; static V g(30), ig(30); if(g.front().a == 0) { modint root = 2; while((root.pow((mod - 1) / 2)).a == 1) root += 1; rep(i, 30) g[i] = -(root.pow((mod - 1) >> (i + 2))), ig[i] = g[i].inv(); } int n = size(f); if(!inv) { for(int m = n; m >>= 1;) { modint w = 1; for(int s = 0, k = 0; s < n; s += 2 * m) { for(int i = s, j = s + m; i < s + m; ++i, ++j) { auto x = f[i], y = f[j] * w; if(x.a >= mod) x.a -= mod; f[i].a = x.a + y.a, f[j].a = x.a + (mod - y.a); } w *= g[__builtin_ctz(++k)]; } } } else { for(int m = 1; m < n; m *= 2) { modint w = 1; for(int s = 0, k = 0; s < n; s += 2 * m) { for(int i = s, j = s + m; i < s + m; ++i, ++j) { auto x = f[i], y = f[j]; f[i] = x + y, f[j].a = x.a + (mod - y.a), f[j] *= w; } w *= ig[__builtin_ctz(++k)]; } } } modint c; if(inv) c = modint(n).inv(); else c = 1; for(auto &&e : f) e *= c; } Poly operator-(Poly f) { for(auto &&e : f) e = -e; return f; } Poly &operator+=(Poly &l, const Poly &r) { l.resize(max(l.size(), r.size())); rep(i, r.size()) l[i] += r[i]; return l; } Poly operator+(Poly l, const Poly &r) { return l += r; } Poly &operator-=(Poly &l, const Poly &r) { l.resize(max(l.size(), r.size())); rep(i, r.size()) l[i] -= r[i]; return l; } Poly operator-(Poly l, const Poly &r) { return l -= r; } Poly &operator<<=(Poly &f, size_t n) { return f.insert(f.begin(), n, 0), f; } Poly operator<<(Poly f, size_t n) { return f <<= n; } Poly &operator>>=(Poly &f, size_t n) { return f.erase(f.begin(), f.begin() + min(f.size(), n)), f; } Poly operator>>(Poly f, size_t n) { return f >>= n; } constexpr int mod0 = 998244353, mod1 = 1300234241, mod2 = 1484783617; using M0 = modint; using M1 = modint; using M2 = modint; template void mul(vector> &l, vector> &r) { int n = size(l), m = size(r), sz = 1 << __lg(2 * (n + m - 1) - 1); l.resize(sz), FMT(l); r.resize(sz), FMT(r); rep(i, sz) l[i] *= r[i]; FMT(l, true); l.resize(n + m - 1); } Poly operator*(const Poly &l, const Poly &r) { if(l.empty() or r.empty()) return Poly(); int n = size(l), m = size(r), sz = 1 << __lg(2 * (n + m - 1) - 1); vector l0(n), r0(m); vector l1(n), r1(m); vector l2(n), r2(m); rep(i, n) l0[i] = l[i].a, l1[i] = l[i].a, l2[i] = l[i].a; rep(i, m) r0[i] = r[i].a, r1[i] = r[i].a, r2[i] = r[i].a; mul(l0, r0), mul(l1, r1), mul(l2, r2); Poly res(n + m - 1); // garner static constexpr M1 inv0 = 613999507; static constexpr M2 inv1 = 1147332803, inv0m1 = 45381342; static constexpr mint m0 = mod0, m0m1 = m0 * mod1; rep(i, n + m - 1) { int y0 = l0[i].a; int y1 = (inv0 * (l1[i] - y0)).a; int y2 = (inv0m1 * (l2[i] - y0) - inv1 * y1).a; res[i] = m0 * y1 + m0m1 * y2 + y0; } return res; } Poly &operator*=(Poly &l, const Poly &r) { return l = l * r; } Poly integ(const Poly &f) { Poly res(f.size() + 1); for(int i = 1; i < (int)res.size(); ++i) res[i] = f[i - 1] / i; return res; } struct Prd { deque deq; Prd() = default; void emplace(const Poly &f) { deq.emplace_back(f); } Poly calc() { if(deq.empty()) return {1}; sort(all(deq), [&](const Poly &f, const Poly &g) { return si(f) < si(g); }); while(deq.size() > 1) { deq.emplace_back(deq[0] * deq[1]); for(int i = 0; i < 2; ++i) deq.pop_front(); } return deq.front(); } }; Poly prd(vector &v) { Prd p; for(auto &e : v) p.emplace(e); return p.calc(); } // Poly deriv(const Poly &f) { // if(f.size() == 0) return Poly(); // Poly res(f.size() - 1); // rep(i, res.size()) res[i] = f[i + 1] * (i + 1); // return res; // } ostream &operator<<(ostream &os, const Poly &a) { for(auto e : a) cout << e.a << " "; return os; } vmint power_table(mint x, int len) { vmint res(len + 1); res[0] = 1; rep(i, len) res[i + 1] = res[i] * x; return res; } } // namespace modular using namespace modular; mint H(int x, int y) { if(x == 0 and y == 0) return 1; return C(x + y - 1, y - 1); } int main() { INT(a, b, x, y); int p = (b + 4) / 4, r = (b + 3) / 4, q = (b + 2) / 4, s = (b + 1) / 4; auto make = [&](int t, int s, int need) { vmint res(a + 1); rep(i, a + 1) { int j = i - need; if(j < 0) continue; if(i + j > a) continue; res[i + j] += H(i, t) * H(j, s); } return res; }; dump(p, q, r, s); auto dp1 = make(p, q, x), dp2 = make(r, s, y); mint ans; // OUT(dp1, dp2); rep2(i, 0, a) { ans += dp1[i] * dp2[a - i]; } OUT(ans); }