#include // #include // using namespace atcoder; // tabaicho see https://boostjp.github.io/tips/multiprec-int.html // #include // using namespace boost::multiprecision; // cpp_int // int128_t // int256_t // int512_t // int1024_t // uint128_t // uint256_t // uint512_t // uint1024_t #define int long long #define inf 1000000007 // #define inf 998244353 #define pa pair #define ppa pair #define ll long long #define PI 3.14159265358979323846 #define mp make_pair #define pb push_back #define EPS (1e-8) using namespace std; int dx[8]={0,1,0,-1,1,1,-1,-1}; int dy[8]={1,0,-1,0,-1,1,1,-1}; class pa3{ public: int x; int y,z; pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {} bool operator < (const pa3 &p) const{ if(x!=p.x) return x (const pa3 &p) const{ if(x!=p.x) return x>p.x; if(y!=p.y) return y>p.y; return z>p.z; //return x != p.x ? x (const pa4 &p) const{ if(x!=p.x) return x>p.x; if(y!=p.y) return y>p.y; if(z!=p.z)return z>p.z; return w>p.w; //return x != p.x ? x (const pa2 &p) const{ return x != p.x ? xb) return Gcd(b,v); if(v==b) return b; if(b%v==0) return v; return Gcd(v,b%v); } int extgcd(int a, int b, int &x, int &y) { if (b == 0) { x = 1; y = 0; return a; } int d = extgcd(b, a%b, y, x); y -= a/b * x; return d; } pa operator+(const pa & l,const pa & r) { return {l.first+r.first,l.second+r.second}; } pa operator-(const pa & l,const pa & r) { return {l.first-r.first,l.second-r.second}; } pair operator-(const pair & l,const pair & r) { return {l.first-r.first,l.second-r.second}; } ostream& operator<<(ostream& os, const vector& VEC){ for(auto v:VEC)os<& PAI){ os<& VEC){ for(auto v:VEC)os<& VEC){ for(auto v:VEC){ os<nn || nn<0) return 0; int r=pr[nn]*inv[rr]; r%=mod; r*=inv[nn-rr]; r%=mod; return r; } void gya(int ert){ pr[0]=1; for(int i=1;i<=ert;i++){ pr[i]=((ll)pr[i-1]*i)%mod; } inv[ert]=beki(pr[ert],mod-2,mod); for(int i=ert-1;i>=0;i--){ inv[i]=(ll)inv[i+1]*(i+1)%mod; } } int beki(int a,int b){ int ANS=1; int be=a%mod; while(b){ if(b&1){ ANS*=be; ANS%=mod; } be*=be; be%=mod; b/=2; } return ANS; } // cin.tie(0); // ios::sync_with_stdio(false); //priority_queue,greater> pq; //sort(ve.begin(),ve.end(),greater()); // mt19937(clock_per_sec); // mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ; // a,b,c : positive int a*b<=c <=> a<=c/b // auto dfs=[&](auto &&self,int r,int p)->int{ // }; class Point{ public: double x,y; Point(double x=0,double y=0):x(x),y(y) {} Point operator + (Point p) {return Point(x+p.x,y+p.y);} Point operator - (Point p) {return Point(x-p.x,y-p.y);} Point operator * (double a) {return Point(x*a,y*a);} Point operator / (double a) {return Point(x/a,y/a);} double absv() {return sqrt(norm());} double norm() {return x*x+y*y;} bool operator < (const Point &p) const{ return x != p.x ? xEPS ? a par,ranks,kosuu; void shoki(int N){ par.resize(N+1,0); ranks.resize(N+1,0); kosuu.resize(N+1,1); for(int i=0;i<=N;i++){ par[i]=i; } } int root(int x){ return par[x]==x ? x : par[x]=root(par[x]); } bool same(int x,int y){ return root(x)==root(y); } bool is_root(int x){ return x==root(x); } void unite(int x,int y){ x=root(x); y=root(y); int xx=kosuu[x],yy=kosuu[y]; if(x==y) return; if(ranks[x] vec; void shoki1(){ vec.resize(2*cor+3, 0); } void shoki2(){ for(int i=cor-1;i>0;i--) vec[i]=vec[2*i]+vec[2*i+1]; } void clear(){ for(int i=0;i<(int)vec.size();i++)vec[i]=0; } void updadd(int x,int w){ //x 項目に w加算 x+=cor; vec[x]+=w; x/=2; while(x){ vec[x]=vec[2*x]+vec[2*x+1]; x/=2; } } void updchan(int x,int w){ //x項目をwに変更 x+=cor; vec[x]=w; while(x){ x/=2; vec[x]=vec[2*x]+vec[2*x+1]; } } // [a,b) int sum(int a,int b){ int hi=0,mi=0; a+=cor,b+=cor; while(a=x)break;//条件を満たさなくなる ima=ima+vec[p]; p++; if(p==(p&(-p))) return cor; } while(1){ if(p>=cor) return p-cor; p*=2; if(ima+vec[p]x)break;//条件を満たさなくなる ima=ima+vec[p]; p++; if(p==(p&(-p))) return cor; } while(1){ if(p>=cor) return p-cor; p*=2; if(ima+vec[p]<=x){//条件を満たす ima+=vec[p]; p++; } } } }; void solve(){ int n,m; cin>>n>>m; gya(500040); int ans=0; { ans=beki(m,2*n)+mod-beki(m-1,2*n); ans%=mod; ans*=m; ans%=mod; } for(int i=2;i-1<=n;i++)if(i<=m){ int ki=beki(i,i-2); int co=comb(n,i-1)*comb(m,i)%mod; int noko=beki(m-i,2*n-2*i+2); int kei=beki(2,i-1)*pr[i-1]%mod; ki*=co; ki%=mod; ki*=noko; ki%=mod; ki*=kei; ki%=mod; ans+=mod-ki; } cout<>n; for(int i=0;i