石子排列（枚举）

#include <iostream>
using namespace std;
const int M = 1000000007 ;
int solve(int n, int m)
{
    if (n == 1)
    {
        return m;
    }
   long long  dp = m;  //卡longlong
    for (int i = 1; i < n; i++)
    {
        dp = dp*(m - 1)%M;
    }
    return dp;
}
int main()
{

    int n, m;
    cin >> n >> m;

    cout << solve(n, m);
    system("pause");
    return 0;
}