#include <iostream>

using namespace std;

int main() {
    int n;
    cin >> n;

    //
    int arr[n];
    int cnt = 0;
    int result = 0

    //
    for (int i  = 0;i < n;i++)
    {
        if(cnt <= 3){
            result =  result - arr[i-1];
        }
        result += arr[i];
        cnt++;
        
    }
    return 0;
}