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#include <bits/stdc++.h>

using namespace std;

constexpr int P = 1000*1000*1000+7;

vector<int> a, b;

inline int A(int n, int m, int k)
{
    int ai1 = a[0];
    a[0] = 0;
    b[0] = 0;
    for (int i = 1; i <= n; i++) {
        int ai = a[i];
        a[i] = int64_t(k) * (a[i - 1] + b[i - 1]) % P;
        b[i] = (int64_t(m - k + 1) * ai1 + int64_t(m - k) * b[i - 1]) % P;
        ai1 = ai;
    }
    return a[n];
}

int main()
{
    int n, m;
    int total = 0;
    scanf("%d%d", &n, &m);
    a.resize(n + 1, 0);
    a[0] = 1;
    b.resize(n + 1, 0);
    for (int k = 1; k <= min(n / 2, m); ++k)
        total = (total + A(n, m, k)) % P;
    printf("%d\n", total);
    return 0;
}