func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 51;   const int mod = (int)1e9 + 7;   long long dp0[N][N];   long long dp1[N][N];   long long C[N][N];   inline long long modpow(long long x, long long p) {     long long res = 1;     while (p) {       if (p & 1) res = res * x % mod;       x = x * x % mod;       p >>= 1;     }     return res;   }   void solve() {     long long i2 = modpow(2, mod - 2);     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;       }     }     memset(dp0, 0, sizeof(dp0));     memset(dp1, 0, sizeof(dp1));     int n, K;     cin >> n >> K;     dp1[0][0] = 1;     dp0[1][0] = 1;     for (int sz = 2; sz <= n; sz++) {       for (int k = 0; k <= sz / 2; k++) {         for (int szl = 0; szl < sz; szl++) {           int szr = sz - 1 - szl;           if (szl > szr) break;           long long enumerate = sz == n ? 1 : sz;           enumerate = enumerate * C[sz - 1][szl] % mod;           for (int kl = 0; kl <= k; kl++) {             if (szl == szr && kl > k - kl) break;             if (szl == szr && kl == k - kl) enumerate = enumerate * i2 % mod;             dp0[sz][k] += dp1[szl][kl] * dp1[szr][k - kl] % mod * enumerate;             dp0[sz][k] %= mod;             dp1[sz][k + 1] += (dp1[szl][kl] * dp0[szr][k - kl] +                                dp0[szl][kl] * dp1[szr][k - kl] +                                dp0[szl][kl] * dp0[szr][k - kl]) %                               mod * enumerate;             dp1[sz][k + 1] %= mod;             if (szl == szr && kl == k - kl) enumerate = enumerate * 2 % mod;           }         }       }     }     cout << (dp0[n][K] + dp1[n][K]) % mod << endl;   }   signed main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     solve();     return 0;   }   