#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<string.h>
using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)
#define eprintf(...) fprintf(stderr, __VA_ARGS__)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }
template<class Iter> void rprintf(const char *fmt, Iter begin, Iter end) {
    for (bool sp=0; begin!=end; ++begin) { if (sp) putchar(' '); else sp = true; printf(fmt, *begin); }
    putchar('\n');
}
template<int MOD>
struct ModInt {
    unsigned x;
    void undef() { x = (unsigned)-1; }
    bool isnan() const { return x == (unsigned)-1; }
    inline int getInt() const { return (int)x; }
    template<class T> T get() const { return (T)x; }
    inline int mod() const { return MOD; }
    ModInt(int y=0) { if (y<0 || MOD<=y) y %= MOD; if (y<0) y += MOD; x=y; }
    ModInt(long long y) { if (y<0 || MOD<=y) y %= MOD; if (y<0) y += MOD; x=y; }
    ModInt(unsigned long long y) { if (MOD<=y) x = y % (unsigned long long)MOD; else x = y; }
    ModInt &operator+=(const ModInt &y) { if ((x += y.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(const ModInt &y) { if ((x += MOD - y.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator*=(const ModInt &y) { x = (unsigned long long)x * y.x % (unsigned long long)MOD; return *this; }
    ModInt &operator/=(const ModInt &y) { x = (unsigned long long)x * y.inv().x % (unsigned long long)MOD; return *this; }
    ModInt operator-() const { return (x ? MOD-x: 0); }
    ModInt inv() const {
	unsigned a = MOD, b = x; int u = 0, v = 1;
	while (b) {
	    int t = a / b;
	    a -= t * b; swap(a, b);
	    u -= t * v; swap(u, v);
	}
	if (u < 0) u += MOD;
	return ModInt(u);
    }
    ModInt pow(long long y) const {
	ModInt b = *this, r = 1;
	if (y < 0) { b = b.inv(); y = -y; }
	for (; y; y>>=1) {
	    if (y&1) r *= b;
	    b *= b;
	}
	return r;
    }
};
const LL MOD = 1000000007;
typedef ModInt<MOD> Mint;
Mint operator+(Mint x, const Mint &y) { if ((x.x += y.x) >= (unsigned)x.mod()) x.x -= x.mod(); return x; }
Mint operator-(Mint x, const Mint &y) { if ((x.x += x.mod() - y.x) >= (unsigned)x.mod()) x.x -= x.mod(); return x; }
Mint operator*(Mint x, const Mint &y) { x.x = (unsigned long long)x.x * y.x % (unsigned long long)x.mod(); return x; }
Mint operator/(Mint x, const Mint &y) { x.x = (unsigned long long)x.x * y.inv().x % (unsigned long long)x.mod(); return x; }
bool operator<(const Mint &x, const Mint &y) { return x.x < y.x; }
bool operator==(const Mint &x, const Mint &y) { return x.x == y.x; }
bool operator!=(const Mint &x, const Mint &y) { return x.x != y.x; }

int N, M;
Mint dp[2][311][311];

int main() {
    scanf("%d%d", &N, &M);
    int cur = 0, nxt = 1;
    dp[0][1][0] = 1;

    REP (t, M) {
	memset(dp[nxt], 0, sizeof dp[nxt]);

	for (int i=1; i<=t+1; i++) REP (j, N) if (dp[cur][i][j].x) {
	    dp[nxt][i+j][0] += dp[cur][i][j] * i;
	    dp[nxt][i][j] += dp[cur][i][j] * j;
	    if (i+j < N) dp[nxt][i][j+1] += dp[cur][i][j] * (N - i - j);
	}

	swap(cur, nxt);
    }

    printf("%d\n", dp[cur][N][0].getInt());

    return 0;
}



Measured memory_bytes: 1152