#include <iostream>
using namespace std;
int main() {
    int num_days, total_money = 0;
    cin >> num_days;
    for (int i = 1; i <= num_days; i++) {
        int buns;
        cin >> buns;
        total_money += buns * i;
    }
    cout << total_money;
    return 0;
}