#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j, a, b;
  int S = 0;
  int choc = 100;
  int carrots;
  int flour = 1;
  int egg = 1;
  cin >> carrots;
  while (carrots--) {
    cin >> choc;
    choc *= flour;
    S += choc;
    flour += egg;
  }
  cout << S << endl;
  return 0;
}
