#include <bits/stdc++.h>
#pragma GCC optimize("-Ofast")
//#pragma GCC optimize("trapv")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#define I inline void
#define S struct
#define vi vector<int>
#define vii vector<pair<int, int>>
#define pii pair<int, int>
#define pll pair<ll, ll>
using namespace std;
using ll = long long;
using ld = long double;
const int N = 2e5 + 7, mod = 1e9 + 7;
const ll inf = 2e18;
// How interesting!
int n, m;
int faspow(int x, int y)
{
if (!y)
return 1;
int ret = faspow(x, y / 2);
ret = 1ll * ret * ret % mod;
if (y & 1)
ret = 1ll * ret * x % mod;
return ret;
}
int eulerian(int n, int m)
{
int ret = 0;
int ncr = 1;
for (int i = 0; i <= m + 1; ++i)
{
int add = 1ll * ncr * faspow(m + 1 - i, n) % mod;
ret = (ret + (i & 1 ? -add : add));
ret = (ret % mod + mod) % mod;
int mul = 1ll * (n + 1 - i) * faspow(i + 1, mod - 2) % mod;
ncr = 1ll * ncr * mul % mod;
}
return ret;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
//freopen("in.in", "r", stdin);
cin >> n >> m;
m -- ;
cout << eulerian(n, m);
return 0;
}
/*
- bounds sir (segtree = 4N, eulerTour = 2N, ...)
- a variable defined twice?
- will overflow?
- is it a good complexity?
- don't mess up indices (0-indexed vs 1-indexed)
- reset everything between testcases.
*/
