// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main() {
    int n;cin>>n;
    vector<array<int,3>> dp(n+1);
    dp[0][0]=1;
    for(int i = 1;i<=n;i++){
        dp[i][0]=dp[i-1][0]+(i>1?dp[i-2][0]+dp[i-2][1]+dp[i-2][2]:0LL);
        dp[i][1]=dp[i-1][2]+dp[i-1][0]+(i>1?dp[i-2][2]:0);
        dp[i][2]=dp[i-1][1]+dp[i-1][0]+(i>1?dp[i-2][1]:0);
    }                    
    cout<<dp[n][0];
}