#include <bits/stdc++.h>
using namespace std;
int groB(int a, int b, int c) {
  if (a == b || b == c) return -1;
  if (b > c && b > a) return 1;
  return 0;
}
int main() {
  int n, t;
  cin >> n >> t;
  int dp[22][11][4][4];
  for (int i = 0; i < 22; i++)
    for (int j = 0; j < 11; j++)
      for (int q = 0; q < 4; q++)
        for (int w = 0; w < 4; w++) dp[i][j][q][w] = 0;
  for (int i = 0; i < 4; i++)
    for (int j = i + 1; j < 4; j++) dp[1][0][i][j] = 1;
  for (int i = 2; i <= n; i++) {
    for (int j = 0; j <= t; j++) {
      for (int f = 0; f < 4; f++)
        for (int s = 0; s < 4; s++) {
          dp[i][j][f][s] = 0;
          for (int tt = 0; tt < 4; tt++) {
            int tmp = groB(tt, f, s);
            if (tmp == -1) continue;
            if (tmp)
              dp[i][j][f][s] += dp[i - 1][j - 1][tt][f];
            else
              dp[i][j][f][s] += dp[i - 1][j][tt][f];
          }
        }
    }
  }
  int res = 0;
  for (int i = 1; i < 4; i++)
    for (int j = 0; j < i; j++) res += dp[n - 1][t][i][j];
  cout << res << endl;
}
