#line 1 "main.cpp" //#pragma GCC target("avx") //#pragma GCC optimize("O3") //#pragma GCC optimize("unroll-loops") #include #ifdef LOCAL #include #define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__) #else #define debug(...) (static_cast(0)) #endif using namespace std; using ll = long long; using ld = long double; using pll = pair; using pii = pair; using vi = vector; using vvi = vector; using vvvi = vector; using vl = vector; using vvl = vector; using vvvl = vector; using vpii = vector; using vpll = vector; using vs = vector; template using pq = priority_queue, greater>; #define overload4(_1, _2, _3, _4, name, ...) name #define overload3(a,b,c,name,...) name #define rep1(n) for (ll UNUSED_NUMBER = 0; UNUSED_NUMBER < (n); ++UNUSED_NUMBER) #define rep2(i, n) for (ll i = 0; i < (n); ++i) #define rep3(i, a, b) for (ll i = (a); i < (b); ++i) #define rep4(i, a, b, c) for (ll i = (a); i < (b); i += (c)) #define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__) #define rrep1(n) for(ll i = (n) - 1;i >= 0;i--) #define rrep2(i,n) for(ll i = (n) - 1;i >= 0;i--) #define rrep3(i,a,b) for(ll i = (b) - 1;i >= (a);i--) #define rrep4(i,a,b,c) for(ll i = (a) + ((b)-(a)-1) / (c) * (c);i >= (a);i -= c) #define rrep(...) overload4(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__) #define all1(i) begin(i) , end(i) #define all2(i,a) begin(i) , begin(i) + a #define all3(i,a,b) begin(i) + a , begin(i) + b #define all(...) overload3(__VA_ARGS__, all3, all2, all1)(__VA_ARGS__) #define sum(...) accumulate(all(__VA_ARGS__),0LL) template bool chmin(T &a, const T &b){ if(a > b){ a = b; return 1; } else return 0; } template bool chmax(T &a, const T &b){ if(a < b){ a = b; return 1; } else return 0; } template auto min(const T& a){return *min_element(all(a));} template auto max(const T& a){return *max_element(all(a));} template void in(Ts&... t); #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__) #define LD(...) ld __VA_ARGS__; in(__VA_ARGS__) #define VEC(type, name, size) vector name(size); in(name) #define VV(type, name, h, w) vector> name(h, vector(w)); in(name) ll intpow(ll a, ll b){ ll ans = 1; while(b){if(b & 1) ans *= a; a *= a; b /= 2;} return ans;} ll modpow(ll a, ll b, ll p){ ll ans = 1; a %= p;if(a < 0) a += p;while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; } ll GCD(ll a,ll b) { if(a == 0 || b == 0) return 0; if(a % b == 0) return b; else return GCD(b,a%b);} ll LCM(ll a,ll b) { if(a == 0) return b; if(b == 0) return a;return a / GCD(a,b) * b;} namespace IO{ #define VOID(a) decltype(void(a)) struct setting{ setting(){cin.tie(nullptr); ios::sync_with_stdio(false);fixed(cout); cout.precision(12);}} setting; template struct P : P{}; template<> struct P<0>{}; template void i(T& t){ i(t, P<3>{}); } void i(vector::reference t, P<3>){ int a; i(a); t = a; } template auto i(T& t, P<2>) -> VOID(cin >> t){ cin >> t; } template auto i(T& t, P<1>) -> VOID(begin(t)){ for(auto&& x : t) i(x); } template void ituple(T& t, index_sequence){ in(get(t)...);} template auto i(T& t, P<0>) -> VOID(tuple_size{}){ ituple(t, make_index_sequence::value>{});} #undef VOID } #define unpack(a) (void)initializer_list{(a, 0)...} template void in(Ts&... t){ unpack(IO :: i(t)); } #undef unpack static const double PI = 3.1415926535897932; template struct REC { F f; REC(F &&f_) : f(forward(f_)) {} template auto operator()(Args &&...args) const { return f(*this, forward(args)...); }}; //constexpr int mod = 1000000007; constexpr int mod = 998244353; #line 2 "library/modint/Modint.hpp" template struct Modint{ int x; Modint():x(0) {} Modint(long long y): x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {} Modint &operator += (const Modint &p) { if((x += p.x) >= mod) x -= mod; return *this;} Modint &operator -= (const Modint &p) { if ((x += mod - p.x) >= mod) x -= mod; return *this;} Modint &operator *= (const Modint &p) { x = (int)(1LL * x * p.x % mod); return *this;} Modint &operator /= (const Modint &p) { *this *= p.inverse(); return *this;} Modint operator -() const{return Modint(-x);} Modint operator +(const Modint &p) const {return Modint(*this) += p;} Modint operator -(const Modint &p) const {return Modint(*this) -= p;} Modint operator *(const Modint &p) const {return Modint(*this) *= p;} Modint operator /(const Modint &p) const {return Modint(*this) /= p;} Modint &operator ++() {if(x == mod - 1) x = 0; else x++; return *this;} Modint &operator --() {if(x == 0) x = mod - 1; else x--; return *this;} bool operator == (const Modint &p) const {return x == p.x;} bool operator != (const Modint &p) const {return x != p.x;} Modint inverse() const { int a = x, b = mod, u = 1, v = 0, t; while (b > 0) { t = a / b; swap(a -= t * b, b); swap(u -= t * v, v); } return Modint(u);} Modint pow(long long n) const { Modint ret(1), mul(x); while (n > 0) { if (n & 1) ret *= mul; mul *= mul; n >>= 1; } return ret;} friend ostream &operator<<(ostream &os, const Modint &p) { return os << p.x; } friend istream &operator>>(istream &is, Modint &a) { long long t; is >> t; a = Modint(t); return (is); } int get() const { return x; } static constexpr int get_mod() {return mod;} }; #line 86 "main.cpp" using mint = Modint; using vm = vector; using vvm = vector; using vvvm = vector; vector fact, fact_inv; void make_fact(int n){ fact.resize(n+1), fact_inv.resize(n+1); fact[0] = mint(1); rep(i,1,n+1) fact[i] = fact[i-1] * mint(i); fact_inv[n] = fact[n].inverse(); rrep(i,0,n) fact_inv[i] = fact_inv[i+1] * mint(i+1); } mint ncr(int n, int r){ if(n < 0 || r < 0 || n < r) return mint(0); return fact[n] * fact_inv[r] * fact_inv[n-r];} mint npr(int n, int r){ if(n < 0 || r < 0 || n < r) return mint(0); return fact[n] * fact_inv[n-r]; } #line 2 "library/data-structure/FenwickTree.hpp" template struct FenwickTree{ int N; vector data; FenwickTree() = default; FenwickTree(int size) {init(size);} void init(int size) { N = size + 2; data.assign(N + 1,{}); } T prod(int k) const { if (k < 0) return T{}; T ret{}; for (++k;k > 0;k -= k & -k) ret += data[k]; return ret; } inline T prod(int l,int r) const {return prod(r - 1) - prod(l - 1);} inline T get(int k) const {return prod(k) - prod(k - 1); } void add(int k, T x) { for(++k;k < N;k += k & -k) data[k] += x; } int lower_bound(T w) { if (w <= 0) return 0; int x = 0; for(int k = 1 <<__lg(N);k;k >>= 1) { if (x + k <= N - 1 && data[x + k] < w) { w -= data[x + k]; x += k; } } return x; } int upper_bound(T w) { if (w < 0) return 0; int x = 0; for(int k = 1 <<__lg(N);k;k >>= 1) { if (x + k <= N - 1 && data[x + k] <= w) { w -= data[x + k]; x += k; } } return x; } }; #line 99 "main.cpp" template ll inv_number(vector &A) { int N = A.size(); ll ans = 0; vector B = A; sort(B.begin(),B.end()); B.erase(unique(B.begin(),B.end()),B.end()); FenwickTree bit(B.size() + 1); for (int i = 0;i < N;i++) { int pos = lower_bound(B.begin(),B.end(),A[i]) - B.begin(); ans += i - bit.prod(pos); bit.add(pos,1); } return ans; } int main() { INT(n,m); make_fact(n); vi p(n); FenwickTree fw1(n),fw2(n+1); rep(i,m) { INT(a,b); a--; p[a] = b; fw1.add(a,-1); fw2.add(b,-1); } rep(i,n) { fw1.add(i,1); fw2.add(i+1,1); } vi tmp; rep(i,n) if(p[i]) tmp.emplace_back(p[i]); ll c = inv_number(tmp); mint ans = npr(n-m,n-m) * c; ans += mint(n-m) * (n-m-1) / 4 * npr(n-m,n-m); rep(i,n) { if(p[i]) { int LC = fw1.prod(0,i); int HP = fw2.prod(p[i],n+1); ans += mint(LC) * HP * npr(n-m-1,n-m-1); int RC = fw1.prod(i,n); int LP = fw2.prod(0,p[i]); ans += mint(RC) * LP * npr(n-m-1,n-m-1); } } cout << ans << '\n'; }