import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.InputMismatchException;
import java.util.PriorityQueue;
import java.util.TreeSet;
public class Main {
InputStream is;
int __t__ = 1;
int __f__ = 0;
int __FILE_DEBUG_FLAG__ = __f__;
String __DEBUG_FILE_NAME__ = "src/F2";
FastScanner in;
PrintWriter out;
/* MOD_CALCULATION */
int MOD = 1_000_000_007;
long ADD(long a, long b) {
return (a + b) % MOD;
}
long SUB(long a, long b) {
return (a - b + MOD) % MOD;
}
long MULT(long a, long b) {
return (a * b) % MOD;
}
long POW(long a, long x) {
long res = 1;
for ( ; x > 0; x >>= 1) {
if (x % 2 == 1) res = MULT(res, a);
a = MULT(a, a);
}
return res;
}
long DIV(long a, long b) {
return MULT(a, POW(b, MOD - 2));
}
/* end */
int MAX = 310;
public void solve() {
int N = in.nextInt(), M = in.nextInt();
long[] fact = new long[MAX];
fact[0] = fact[1] = 1;
for (int i = 2; i < MAX; i++) {
fact[i] = MULT(fact[i-1], i);
}
long[][][] dp = new long[M+1][N+1][N+1];
dp[0][1][0] = 1;
for (int i = 0; i < M; i++) {
for (int j = 1; j <= N; j++) {
for (int k = 0; k <= N; k++) {
if (dp[i][j][k] == 0) continue;
dp[i+1][j][k] = ADD(dp[i+1][j][k], MULT(dp[i][j][k], k));
if (j + k <= N)
dp[i+1][j+k][0] = ADD(dp[i+1][j+k][0], MULT(dp[i][j][k], j));
if (k + 1 <= N)
dp[i+1][j][k+1] = ADD(dp[i+1][j][k+1], MULT(dp[i][j][k], N - j - k));
}
}
}
System.out.println(dp[M][N][0]);
}
public void run() {
if (__FILE_DEBUG_FLAG__ == __t__) {
try {
is = new FileInputStream(__DEBUG_FILE_NAME__);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
System.out.println("FILE_INPUT!");
} else {
is = System.in;
}
in = new FastScanner(is);
out = new PrintWriter(System.out);
Thread t = new Thread(null, new Runnable() {
@Override
public void run() {
solve();
}
}, "lul", 1 << 30);
t.start();
}
public static void main(String[] args) {
new Main().run();
}
public void mapDebug(int[][] a) {
System.out.println("--------map display---------");
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
System.out.printf("%3d ", a[i][j]);
}
System.out.println();
}
System.out.println("----------------------------");
System.out.println();
}
public void debug(Object... obj) {
System.out.println(Arrays.deepToString(obj));
}
class FastScanner {
private InputStream stream;
private byte[] buf = new byte[1024];
private int curChar;
private int numChars;
public FastScanner(InputStream stream) {
this.stream = stream;
//stream = new FileInputStream(new File("dec.in"));
}
int read() {
if (numChars == -1)
throw new InputMismatchException();
if (curChar >= numChars) {
curChar = 0;
try {
numChars = stream.read(buf);
} catch (IOException e) {
throw new InputMismatchException();
}
if (numChars <= 0)
return -1;
}
return buf[curChar++];
}
boolean isSpaceChar(int c) {
return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
}
boolean isEndline(int c) {
return c == '\n' || c == '\r' || c == -1;
}
int nextInt() {
return Integer.parseInt(next());
}
int[] nextIntArray(int n) {
int[] array = new int[n];
for (int i = 0; i < n; i++)
array[i] = nextInt();
return array;
}
int[][] nextIntMap(int n, int m) {
int[][] map = new int[n][m];
for (int i = 0; i < n; i++) {
map[i] = in.nextIntArray(m);
}
return map;
}
long nextLong() {
return Long.parseLong(next());
}
long[] nextLongArray(int n) {
long[] array = new long[n];
for (int i = 0; i < n; i++)
array[i] = nextLong();
return array;
}
long[][] nextLongMap(int n, int m) {
long[][] map = new long[n][m];
for (int i = 0; i < n; i++) {
map[i] = in.nextLongArray(m);
}
return map;
}
double nextDouble() {
return Double.parseDouble(next());
}
double[] nextDoubleArray(int n) {
double[] array = new double[n];
for (int i = 0; i < n; i++)
array[i] = nextDouble();
return array;
}
double[][] nextDoubleMap(int n, int m) {
double[][] map = new double[n][m];
for (int i = 0; i < n; i++) {
map[i] = in.nextDoubleArray(m);
}
return map;
}
String next() {
int c = read();
while (isSpaceChar(c))
c = read();
StringBuilder res = new StringBuilder();
do {
res.appendCodePoint(c);
c = read();
} while (!isSpaceChar(c));
return res.toString();
}
String[] nextStringArray(int n) {
String[] array = new String[n];
for (int i = 0; i < n; i++)
array[i] = next();
return array;
}
String nextLine() {
int c = read();
while (isEndline(c))
c = read();
StringBuilder res = new StringBuilder();
do {
res.appendCodePoint(c);
c = read();
} while (!isEndline(c));
return res.toString();
}
}
}