#include <bits/stdc++.h>   using namespace std;   const int MAXN = 25;   int dp[MAXN][MAXN][MAXN];   int n, t;   int main() {     scanf( %d%d , &n, &t);     t = 2 * t;     dp[1][0][1] = dp[1][0][2] = dp[1][0][3] = 1;     for (int i = 1; i < n; ++i)       for (int j = 0; j <= t; ++j)         for (int k = 1; k <= 4; ++k)           for (int l = 1; l <= 4; ++l) {             if ((i == 1 && l > k) || (i != 1 && l != k)) {               int nj = j;               if (j % 2 && l < k)                 ++nj;               else if (j % 2 == 0 && l > k)                 ++nj;               dp[i + 1][nj][l] += dp[i][j][k];             }           }     int ans = 0;     for (int i = 1; i <= 4; ++i) ans += dp[n][t][i];     printf( %d n , ans);     return 0;   }   