#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
//#define ll __int128
//#define int ll
//#dLefine char ll
//#define double ld
typedef vector<char> vc;
typedef vector <vc> vvc;
typedef vector <vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector <int> vi;
typedef vector <pii> vpi;
typedef vector <vi> vvi;
typedef vector <vvi> vvvi;
typedef vector<short> vs;
typedef vector <vs> vvs;
typedef vector <vvs> vvvs;
typedef vector <ll> vl;
typedef vector <vl> vvl;
typedef vector <vvl> vvvl;
typedef vector <ld> vld;
typedef vector <vld> vvld;
typedef vector <vvld> vvvld;
typedef vector <string> vst;
typedef vector <vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";


template<class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template<class T0, class T1>
inline istream &operator>>(istream &in, pair<T0, T1> &a) {
    return in >> a.first >> a.second;
}

template<class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template<class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " << get<3>(a) << "}";
}

template<class T>
inline ostream &operator<<(ostream &out, vector <T> &a) {
    out << "[";
    fori (i, a.size())out << a[i] << vector < string > {", ", "]  "}[i + 1 == a.size()];
    return out;
}


void smain();


signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
#ifdef MAX_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#endif
#ifdef HK_CUP
    freopen("finput.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    cout << setprecision(12) << fixed;
    smain();
#ifdef MAX_HOME
#ifndef HK_CUP
    cout << "\n\nTOTAL EXECUTION TIME: " << float(clock() - start) / CLOCKS_PER_SEC << endl;
#endif
#endif
    return 0;
}

const int N = 303;
const int M = 1e9 + 7;

int dp[N][N][N];

void insum(int &a, int b) {
    a = (a + b) % M;
}

void smain() {
    int n, m;
    cin >> n >> m;
    dp[0][0][1] = 1;
    fori (i, m + 1) {
        fori (cnt_cur, n + 1) {
            fori (cnt_in, n + 1) if (dp[i][cnt_cur][cnt_in]){
                /*inside cur*/;
                insum(dp[i + 1][cnt_cur][cnt_in], (ll) dp[i][cnt_cur][cnt_in] * cnt_cur % M);
                /*outside cur*/;
                insum(dp[i + 1][cnt_cur + 1][cnt_in], (ll) dp[i][cnt_cur][cnt_in] * (n - cnt_in - cnt_cur) % M);
                /*inside in */;
                insum(dp[i + 1][0][cnt_in + cnt_cur], (ll) dp[i][cnt_cur][cnt_in] * cnt_in % M);

//                cerr << "dp[" << i << "][" << cnt_cur << "][" << cnt_in << "] = " << dp[i][cnt_cur][cnt_in] << endl;
            }
        }
    }
    cout << dp[m][0][n];
}

Measured memory_bytes: 58600