How-many

#include <bits/stdc++.h>
#define int long long
using namespace std ; 
const int mod = 1e9 + 7 ; 
inline int read() {
	int x = 0 , f = 1 ; 
	char c = getchar() ; 

	while (c < '0' || c > '9') {
		if (c == '-') f = -f ; 

		c = getchar() ; 
	}

	while (c >= '0' && c <= '9') {
		x = x * 10 + c - '0' ; 
		c = getchar() ; 
	}

	return x * f ; 
}

int N , M ; int dp[52][52] , g[52][52][52] , f[52] ;  
int C[52][52] ; 

int Quick_Pow(int a , int b) {
	int ans = 1 ; 

	while (b) {
		if (b & 1) ans = (ans * a) % mod ; 

		a = (a * a) % mod ; b >>= 1 ; 
	}

	return ans ; 
}

signed main() {
    #ifndef ONLINE_JUDGE
        freopen("1.in" , "r" , stdin) ; 
		freopen("1.out" , "w" , stdout) ; 
    #endif
	N = read() , M = read() ; 

	C[0][0] = 1 ; 
	for (int i = 1 ; i <= N ; ++ i) {
		C[i][0] = 1 ; 

		for (int j = 1 ; j <= i ; ++ j) {
			C[i][j] = (C[i - 1][j] + C[i - 1][j - 1]) % mod ; 
		}
	}

	f[1] = 1 ; dp[1][0] = 1 ; 
	g[1][0][1] = 1 ; 

	for (int n = 2 ; n <= N ; ++ n) {
		f[n] = Quick_Pow(2 , C[n][2]) ; 

		for (int j = 1 ; j < n ; ++ j)
			f[n] = (f[n] + mod - (((C[n - 1][j - 1] * f[j]) % mod) * Quick_Pow(2 , C[n - j][2])) % mod) % mod ; 
		cerr << f[n] << '\n' ; 

		for (int k = 1 ; k <= n ; ++ k) {
			for (int j = 0 ; j <= n - k ; ++ j) {
				for (int i = 1 ; i <= n - k + 1 ; ++ i) {
					for (int x = 0 ; x <= min(j , i - 1) ; ++ x) {
						g[n][j][k] = (g[n][j][k] + ((C[n - 1][i - 1] * dp[i][x]) % mod) * (g[n - i][j - x][k - 1] * i) % mod) % mod ; 
					}
				}
			}
		}

		for (int j = 1 ; j <= n - 1 ; ++ j) {
			for (int i = 1 ; i <= n - j ; ++ i) {
				for (int x = 1 ; x <= j ; ++ x) {
					dp[n][j] = (dp[n][j] + (((dp[i][0] * g[n - i][j - x][x]) % mod) * Quick_Pow(i , x)) % mod) % mod ; 
				}
			}
		}

		dp[n][0] = f[n] ; 
		for (int j = 1 ; j <= n - 1 ; ++ j) {
			dp[n][0] = (dp[n][0] + mod - dp[n][j]) % mod ; 
		}

		cerr << '\n' ; 
	}

	int ans = 0 ; 

	for (int j = 1 ; j <= M ; ++ j) {
		ans = (ans + dp[N][j]) % mod ; 
	}

	printf("%lld" , ans) ; 
}