#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#define N 305
#define int long long
#define ul unsigned long long
#define db double
#define fo(i,l,r) for(int i=l;i<=r;i++)
#define rf(i,r,l) for(int i=r;i>=l;i--)
using namespace std;
int n,m,f[N][N][N];const int mod=1e9+7; 
void swap(int &x,int &y){int t=x;x=y;y=t;}
int max(int x,int y){return x>y?x:y;}
int min(int x,int y){return x<y?x:y;}
int read(){
	int sum=0;bool f=0;char c=getchar();
	for(;c<48||c>57;c=getchar())if(c==45)f=1;
	for(;c>=48&&c<=57;c=getchar())sum=sum*10+(c&15);
	return f?-sum:sum;
}
signed main(){
	freopen("rotk.in","r",stdin);freopen("rotk.out","w",stdout);
	n=read();m=read();
	f[0][1][1]=1;
	fo(i,0,m-1)
		fo(j,1,n)
			fo(k,1,n)
			{
				f[i+1][j+1][k]=(f[i+1][j+1][k]+f[i][j][k]*(n-j))%mod;
				f[i+1][j][k]=(f[i+1][j][k]+f[i][j][k]*(j-k))%mod;
				f[i+1][j][j]=(f[i+1][j][j]+f[i][j][k]*k)%mod;
			}
	printf("%lld",f[m][n][n]);
	return 0;
}