func_code_string: #include <bits/stdc++.h>   int ways[37 * 2 + 1][37 * 2 + 1], k;   void init() {     int i, j;     ways[0][0] = 1;     for (i = 0; i <= k * 2; i++)       for (j = 0; j <= k * 2; j++)         ways[i][j] =             i == 0 || j == 0 ? 1 : (ways[i - 1][j] + ways[i][j - 1]) % 998244353;   }   int oo[1 + (4000 - 1) * 4], oj[1 + (4000 - 1) * 4];   int link(int o, int j) {     static int _ = 1;     oo[_] = o, oj[_] = j;     return _++;   }   int *ae, *xx, dp[4000][37 + 1], dq[4000][37 + 1];   void dfs(int p, int i) {     int o, l, c;     memset(dq[i], 0, (k + 1) * sizeof *dq[i]);     for (o = ae[i]; o; o = oo[o]) {       int j = oj[o];       if (j != p) {         dfs(i, j);         for (l = 0; l <= k; l++) dq[i][l] = (dq[i][l] + dp[j][l]) % 998244353;       }     }     xx[0] = (xx[0] + 1) % 998244353;     memset(dp[i], 0, (k + 1) * sizeof *dp[i]), dp[i][0] = 1;     for (l = 1; l <= k; l++)       for (c = 1; c <= l; c++) {         int x = (long long)dq[i][c - 1] * dp[i][l - c] % 998244353;         dp[i][l] = (dp[i][l] + x) % 998244353;         xx[l] = (xx[l] + (long long)x * c * 2) % 998244353;       }   }   int main() {     static int ae1[4000], xx1[37 + 1], ae2[4000], xx2[37 + 1];     int n1, n2, h, i, j, l, ans;     scanf( %d%d%d , &n1, &n2, &k);     if (k % 2 != 0) {       printf( 0 n );       return 0;     }     k /= 2;     init();     for (h = 0; h < n1 - 1; h++) {       scanf( %d%d , &i, &j), i--, j--;       ae1[i] = link(ae1[i], j), ae1[j] = link(ae1[j], i);     }     for (h = 0; h < n2 - 1; h++) {       scanf( %d%d , &i, &j), i--, j--;       ae2[i] = link(ae2[i], j), ae2[j] = link(ae2[j], i);     }     ae = ae1, xx = xx1, dfs(-1, 0);     ae = ae2, xx = xx2, dfs(-1, 0);     ans = 0;     for (l = 0; l <= k; l++) {       assert(xx1[l] > 0);       ans = (ans + (long long)xx1[l] * xx2[k - l] % 998244353 *                        ways[l * 2][(k - l) * 2]) %             998244353;     }     printf( %d n , ans);     return 0;   }   