text: #include <iostream>
  using namespace std;
  
  long long dp[117];
  
  int main()
  {
  	int n;
  
  	cin >> n;
  	dp[0] = dp[1] = dp[2] = dp[3] = 1;
  	for (int i=4; i<=n; ++i)
  		dp[i] = dp[i-1] + dp[i-3];
  
  	cout << dp[n] << '\n';
  
  	return 0;
  }
  