func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long N = 507;   const long long INF = 1e9 + 7;   long long n, m, mod;   long long Pow(long long x, long long y) {     long long ans = 1, now = x;     while (y) {       if (y & 1) ans = ans * now % mod;       now = now * now % mod;       y >>= 1;     }     return ans;   }   long long fac[N], inv[N], f[N], g[N], F[N][N], G[N][N];   long long C(long long x, long long y) {     return fac[x] * inv[y] % mod * inv[x - y] % mod;   }   int main() {     scanf( %lld%lld%lld , &n, &m, &mod);     fac[0] = 1;     for (long long i = 1; i <= n; i++) fac[i] = fac[i - 1] * i % mod;     inv[n] = Pow(fac[n], mod - 2);     for (long long i = n; i; i--) inv[i - 1] = inv[i] * i % mod;     f[0] = 1;     for (long long i = 1; i <= n; i++) {       f[i] = g[i] = 0;       for (long long j = 1; j <= i; j++) {         f[i] =             (f[i] + f[j - 1] * f[i - j] % mod * C(i - 1, j - 1) % mod * (i + 1)) %             mod;         g[i] =             (g[i] + f[j - 1] * g[i - j] % mod * C(i - 1, j - 1) % mod * (i + 1)) %             mod;         g[i] =             (g[i] + g[j - 1] * f[i - j] % mod * C(i - 1, j - 1) % mod * (i + 1)) %             mod;         g[i] = (g[i] + f[j - 1] * f[i - j] % mod * C(i - 1, j - 1) % mod *                            ((j - 1) * j / 2 + (i - j) * (i - j + 1) / 2)) %                mod;       }     }     F[0][0] = 1;     for (long long i = 1; i <= n; i++) {       F[i][i] = f[i];       G[i][i] = g[i];     }     for (long long i = 0; i <= n - 1; i++) {       for (long long j = 0; j <= m + 1 - 1; j++) {         F[i + 1][j] = (F[i + 1][j] + F[i][j]) % mod;         G[i + 1][j] = (G[i + 1][j] + G[i][j]) % mod;         for (long long k = 1; k <= n; k++) {           if (j + k > m || i + k + 1 > n) break;           F[i + k + 1][j + k] =               (F[i + k + 1][j + k] + F[i][j] * f[k] % mod * C(j + k, k)) % mod;           G[i + k + 1][j + k] =               (G[i + k + 1][j + k] +                (G[i][j] * f[k] + F[i][j] * g[k]) % mod * C(j + k, k)) %               mod;         }       }     }     printf( %lld n , G[n][m]);     return 0;   }   