#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
using namespace std;
typedef long long ll;
vector<ll> ans(100005, 1); long long M = 1e9 + 7;
map<pair<ll, ll>, ll> cmb;

long long qpow(long long a, long long n) {
    long long ret = 1;
    a = (a % M + M) % M;
    for (; n; n >>= 1) {
        if (n & 1) ret = (ret * a) % M;
        a = (a * a) % M;
    }
    return ret;
}


ll comp(ll a,ll b,ll p)//composite num C(a,b)%p
{
    if (cmb.count(make_pair(a,b))) return cmb[make_pair(a, b)];
    if (cmb.count(make_pair(a,a-b))) return cmb[make_pair(a, a-b)];
	if(a<b)return 0;
	if(a==b)return 1;
	if(b>a-b)b=a-b;
	int ans=1,ca=1,cb=1;
	for(ll i=0;i<b;i++)
	{
		ca=(ca*(a-i))%p;
		cb=(cb*(b-i))%p;
	}
	ans=(ca*qpow(cb,p-2))%p;
	cmb[make_pair(a, b)] = ans;
    return ans;
}

int main()
{
    int n, m;
    cin >> n >> m;
    ans[1] = m;
    ans[n] = qpow(m, n);
    int k = -1;
    for (int j = 1; j < m; ++j) {
        ans[n] += k * qpow(j, n) * comp(m, j, M) % M;
        ans[n] = (ans[n] + M) % M;
        k *= -1;
    }
    cout << ans[n] << endl;
    return 0;
}