func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 505;   const int mod = 1000000007;   int a, b, c, d, e, f, g, h, i, j;   int Mi[N * N];   int F[N][N], K;   void Work() {     Mi[0] = 1;     for (int ii = 1; ii <= a * a; ii++) Mi[ii] = (Mi[ii - 1] << 1) % mod;     F[0][0] = 1;     for (int ii = 1; ii <= a; ii++)       for (int jj = 1; jj <= K; jj++) {         for (int kk = 0; kk < ii; kk++)           (F[ii][jj] += (long long)F[kk][jj - 1] * (Mi[ii - kk] - 1) % mod *                         (Mi[(ii - kk) * kk]) % mod) %= mod;       }     int an = 0;     for (int ii = 0; ii <= a; ii++)       (an += (long long)F[ii][K] * Mi[(a - ii) * ii] % mod) %= mod;     cout << an << endl;   }   int main() {     cin >> a >> K;     Work();     return 0;   }   