#include <bits/stdc++.h>
using namespace std;
long long f[22][22][22][3][4];
int sgn(int x) { return x < 0 ? -1 : x > 0; }
int main() {
  int n, t;
  cin >> n >> t;
  for (int i = 0; i < 3; ++i) {
    f[1][0][0][1][i] = 1;
  }
  for (int i = 1; i < n; ++i) {
    for (int j = 0; j <= t; ++j) {
      for (int k = 0; k < t; ++k) {
        for (int eq = 0; eq < 3; ++eq) {
          for (int lst = 0; lst < 4; ++lst) {
            if (!f[i][j][k][eq][lst]) {
              continue;
            }
            for (int cur = 0; cur < 4; ++cur) {
              if (cur == lst) {
                continue;
              }
              int leq = eq - 1;
              int req = sgn(cur - lst);
              if (leq > 0 && req < 0) {
                f[i + 1][j + 1][k][req + 1][cur] += f[i][j][k][eq][lst];
              } else if (leq < 0 && req > 0) {
                f[i + 1][j][k + 1][req + 1][cur] += f[i][j][k][eq][lst];
              } else {
                f[i + 1][j][k][req + 1][cur] += f[i][j][k][eq][lst];
              }
            }
          }
        }
      }
    }
  }
  long long res = 0;
  for (int eq = 0; eq < 3; ++eq) {
    for (int i = 0; i < 4; ++i) {
      res += f[n][t][t - 1][eq][i];
    }
  }
  cout << res << endl;
}
