Task 9

#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main() {
    int n;
    int sum = 0;
    int sum_max = 0;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    for(int i = 0; i<n && i<3; i++){
        sum += a[i];
    }
    sum_max = sum;
    for (int i = 3; i < n; i++) {
        sum = sum - a[i-3] + a[i];
        if(sum>sum_max){
            sum_max = sum;
        }
    }
    cout << sum_max;
    return 0;
}