bunny_not_finished

#include <cstdio>
#include <vector>

#define ULL unsigned long long
#define UINT unsigned int

int main(void) {
  UINT n, k;
  scanf("%u", &n);
  scanf("%u", &k);
  std::vector<unsigned long long> dp(n + 1, 1ULL);
  dp[0] = 1ULL;
  dp[1] = 1ULL;
  for (UINT i = 2; i <= k; i++) {
    for (UINT i = 2; i <= k; i++) {
      dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
    }
  }

  for (UINT i = 3; i <= n; i++) {
    dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
  }

  printf("%llu\n", dp[n]);

  return 0;
}