#include<bits/stdc++.h>
#define int long long
using namespace std;

const int N=3e2+3,mod=1e9+7;
int n,m,f[N][N][N];

signed main(){
	freopen("rotk.in","r",stdin);
	freopen("rotk.out","w",stdout);
	ios::sync_with_stdio(0);
	cin.tie(0);cout.tie(0);
	cin>>n>>m;
	f[0][1][1]=1;
	for(int i(0);i<=m;++i){
		for(int j(1);j<=n;++j){
			for(int k(1);k<=j;++k){
				f[i+1][j][k]=(f[i+1][j][k]+f[i][j][k]*(j-k)%mod)%mod;
				f[i+1][j][j]=(f[i+1][j][j]+f[i][j][k]*k%mod)%mod;
				f[i+1][j+1][k]=(f[i+1][j+1][k]+f[i][j][k]*(n-j)%mod)%mod;
			}
		}
	}
	cout<<f[m][n][n]<<"\n";
	return 0;
}