1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
#include <bits/stdc++.h>
#define mod 1000000007
using namespace std;

long long dp[3000][3000];

long long sp_mod(long long a, long long b)
{
	long long w = 1;
	
	while(b != 0)
	{
		if(b%2 == 1)
        {
            w *= a;
            w %= mod;
    	}
    	
        a %= mod;
		a *= a;
		a %= mod;
		
		b >>= 1;
	}
	return w;
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	int n, m;
	cin >> n >> m;
	
	for(int i = 0; i < n-1; ++i) dp[i][i+1] = m;
	
	for(int i = 2; i < n; ++i) for(int j = 0; j < n-i; ++j)
	{
		for(int k = j+1; k < i+j-1; ++k)
		{
			dp[j][j+i] += (dp[j][k] * sp_mod(m, i+j-k-1))%mod;
			dp[j][j+i] %= mod;
		}
		dp[j][j+i] += sp_mod(m, i) - dp[j+1][j+i-1];
		dp[j][j+i] += mod;
		dp[j][j+i] %= mod;
	}
	
	cout << dp[0][n-1];
	
	return 0;
}