#include <iostream>
#include <vector>

int main() {
    int n;
    std::cin >> n;
    
    std::vector<unsigned long long> dp(n + 1);
    dp[0] = 1;
    
    for (int i = 1; i <= n; i++) {
        dp[i] = dp[i - 1];
        
        if (i >= 2) {
            dp[i] += dp[i - 2];
        }
        
        if (i >= 3) {
            dp[i] += dp[i - 3] * 2;
        }
        
        if (i >= 4) {
            dp[i] += dp[i - 3] * 2;
        }
    }
    
    std::cout << dp[n] << std::endl;
    
    return 0;
}