#include <bits/stdc++.h>
using namespace std;
int main() {
  const int calories = 0;
  int flour = 1;
  int egg = 1;
  int bowl;
  int carrots;
  int spread;
  bowl = calories;
  cin >> carrots;
  for (int c = 1; c <= carrots; c++) {
    cin >> spread;
    bowl += c * spread;
  }
  cout << bowl << endl;
  return 0;
}
