#include <bits/stdc++.h>
using namespace std;
int main() {
  long long dp[25][15][15][4][2] = {0};
  int n, t;
  cin >> n >> t;
  for (int i = 0; i < 4; ++i) dp[0][0][0][i][0] = 1;
  for (int i = 1; i < n; ++i)
    for (int j1 = 0; j1 <= t; ++j1)
      for (int j2 = 0; j2 <= t - 1; ++j2)
        for (int ld = 0; ld < 4; ++ld)
          for (int lf = 0; lf < 2; ++lf)
            for (int x = 0; x < 4; ++x) {
              if (x == ld) continue;
              int f = (x > ld);
              if (i == 1)
                dp[i][j1][j2][x][f] += dp[i - 1][j1][j2][ld][lf];
              else {
                if (lf == 1 && f == 0) {
                  if (j1 > 0)
                    dp[i][j1][j2][x][f] += dp[i - 1][j1 - 1][j2][ld][lf];
                } else if (lf == 0 && f == 1) {
                  if (j2 > 0)
                    dp[i][j1][j2][x][f] += dp[i - 1][j1][j2 - 1][ld][lf];
                } else {
                  dp[i][j1][j2][x][f] += dp[i - 1][j1][j2][ld][lf];
                }
              }
            }
  long long ans = 0;
  for (int ld = 0; ld < 4; ++ld)
    for (int lf = 0; lf < 2; ++lf) ans += dp[n - 1][t][t - 1][ld][lf];
  cout << ans << endl;
  return 0;
}
