#define ATCODER #define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using ld = long double; using pll = pair; using pdd = pair; //template using pq = priority_queue, greater>; #define FOR(i, a, b) for(ll i=(a); i<(b);i++) #define REP(i, n) for(ll i=0; i<(n);i++) #define ROF(i, a, b) for(ll i=(b-1); i>=(a);i--) #define PER(i, n) for(ll i=n-1; i>=0;i--) #define REPREP(i,j,a,b) for(ll i=0;i > #define VV2(type,n,m,val) vector< vector > val;val.resize(n);for(ll i;i #define VEC(type,n,val) vector val;val.resize(n) #define VL vector #define VVL vector< vector > #define VP vector< pair > #define SZ size() #define all(i) begin(i),end(i) #define SORT(i) sort(all(i)) #define BITI(i) (1<>i) & 1) != 0) #define ALLBIT(n) (ll(1)<v?v:n #define MP(a,b) make_pair(a,b) #define DET2(x1,y1,x2,y2) x1*y2-x2*y1 #define DET3(x1,y1,z1,x2,y2,z2,x3,y3,z3) x1*y2*z3+x2*y3*z1+x3*y1*z2-z1*y2*x3-z2*y3*x1-z3*y1*x2 #define INC(a) for(auto& v:a)v++; #define DEC(a) for(auto& v:a)v--; #define SQU(x) (x)*(x) #define L0 ll(0) #ifdef ATCODER #include using namespace atcoder; using mint = modint1000000007; using mint2 = modint998244353; #endif template vector read(size_t n) { vector ts(n); for (size_t i = 0; i < n; i++) cin >> ts[i]; return ts; } template void read_tuple_impl(TV&) {} template void read_tuple_impl(TV& ts) { get(ts).emplace_back(*(istream_iterator(cin))); read_tuple_impl(ts); } template decltype(auto) read_tuple(size_t n) { tuple...> ts; for (size_t i = 0; i < n; i++) read_tuple_impl(ts); return ts; } using val = ll; using func = ll; val op(val a, val b) { return min(a, b); } val e() { return 1e18; } //val mp(func f, val a) { // return MP(a.first + f * a.second, a.second); //} func comp(func f, func g) { return f + g; } func id() { return 0; } ll di[4] = { 1,0,-1,0 }; ll dj[4] = { 0,1,0,-1 }; ll si[4] = { 0,3,3,0 }; ll sj[4] = { 0,0,3,3 }; //ll di[4] = { -1,-1,1,1 }; //ll dj[4] = { -1,1,-1,1 }; ll di8[8] = { 0,-1,-1,-1,0,1,1,1 }; ll dj8[8] = { -1,-1,0,1,1,1,0,-1 }; void solve() { ll n, q; cin >> n >> q; vector c(n); vector f(n * 2 + 100, 1); REP(i, n * 2) f[i + 1] = f[i] * (i + 1); if (n == 1) { cout << q; return; } //PER(i, n) { // REP(j, n - i) { // //i+1以上をj+1個並べる // c[i] += f[n - i] / f[n - i - j - 1] * f[n - j]; // } // //i+1以上が //} //REP(i, n) // cout << c[i].val() << " "; //REP(i, n - 1) // c[i] -= c[i + 1]; //REP(i, n) { // assert(c[i] == f[n + 2] / ((i + 2) * (i + 3))); //} REP(i, n) c[i] = f[n + 2] / ((i + 2) * (i + 3)); mint2 sum = 0; REP(i, n) sum += (i + 1) * c[i]; sum *= mint2(n * (n + 1) / 2).pow(q - 1) * q; cout << sum.val(); return; } int main() { ll t = 1; ///cin >> t; while (t--) { solve(); } return 0; }