#include <iostream>
using namespace std;
int main() {
    int arr[5];
    for(int i = 0; i < 5; i++) {
        cin >> arr[i];
    }
    int sum = 0;
    for(int i = 1; i < 5; i += 2) {
        sum += arr[i];
    }
    cout << sum << endl;
    return 0;
}