#include <bits/stdc++.h> #define N 200030 #define mod 1000000007 using namespace std; typedef long long ll; ll n, m, ans, pot[N], fat[N]; ll Pow(ll x, ll p) { if(!p) return 1LL; ll ans = Pow(x, p/2); ans = (ans*ans)%mod; if(p & 1) return (ans*x)%mod; return ans; } ll inverse(ll x){ return Pow(x, mod - 2)%mod; } ll Choose(ll a, ll b) { ll B = (fat[b]*fat[a - b])%mod; return (fat[a]*inverse(B))%mod; } int32_t main() { ios::sync_with_stdio(false); cin.tie(0); cin>>n>>m; pot[0] = fat[0] = 1; m--; for(int i = 1; i < N; i++) fat[i] = (i*fat[i - 1])%mod; for(int k = 0; k <= m + 1; k++) { ll sign = (k%2 == 0 ? 1 : -1); ans = (ans + ((sign*Choose(n + 1, k)*Pow(m + 1 - k, n))%mod) )%mod; } cout<<(mod + ans)%mod<<'\n'; }