#include <bits/stdc++.h>
using namespace std;
const int maxn = 20 + 5;
const int maxt = 10 + 2;
const int maxy = 5;
int dp[maxn][maxy][maxt][3];
int n, t;
inline int solve(int X, int Y, int T, int H) {
  if (T < 0) return 0;
  int &ret = dp[X][Y][T][H];
  if (ret > -1) return ret;
  if (X == n - 1)
    if (T == 0 && H == 0)
      return ret = Y - 1;
    else
      return ret = 0;
  if (Y == 4 && H == 1) return ret = 0;
  if (Y == 1 && H == 0) return ret = 0;
  ret = 0;
  if (H == 0)
    for (int i = Y - 1; i >= 1; --i)
      ret += solve(X + 1, i, T, 0) + solve(X + 1, i, T, 1);
  if (H == 1)
    for (int i = Y + 1; i <= 4; ++i)
      ret += solve(X + 1, i, T - 1, 0) + solve(X + 1, i, T, 1);
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  memset(dp, -1, sizeof dp);
  cin >> n >> t;
  int ans = 0;
  for (int i = 1; i <= 4; ++i) ans += solve(1, i, t, 1);
  cout << ans << endl;
  return 0;
}
