#include <bits/stdc++.h>
using namespace std;
int n, t, dp[23][23][23][4][4];
int dfs(int x, int h, int l, int pp, int p) {
  if (dp[x][h][l][pp][p] != -1) return dp[x][h][l][pp][p];
  if (x == n) {
    if (h == t && l == t - 1)
      return 1;
    else
      return 0;
  }
  dp[x][h][l][pp][p] = 0;
  for (int i = 0; i < 4; i++)
    if (p != i)
      if (pp != 233) {
        if (pp < p && p > i)
          dp[x][h][l][pp][p] += dfs(x + 1, h + 1, l, p, i);
        else if (pp > p && p < i)
          dp[x][h][l][pp][p] += dfs(x + 1, h, l + 1, p, i);
        else
          dp[x][h][l][pp][p] += dfs(x + 1, h, l, p, i);
      } else
        dp[x][h][l][pp][p] += dfs(x + 1, h, l, p, i);
  return dp[x][h][l][pp][p];
}
int main() {
  for (int i = 0; i < 23; i++)
    for (int j = 0; j < 23; j++)
      for (int k = 0; k < 23; k++)
        for (int l = 0; l < 4; l++)
          for (int o = 0; o < 4; o++) dp[i][j][k][l][o] = -1;
  cin >> n >> t;
  cout << dfs(0, 0, 0, 233, 233);
}
