#include <bits/stdc++.h>
using namespace std;
bool prost(int a) {
  for (int i = 2; i * i <= a; i++) {
    if (a % i == 0) return false;
  }
  return true;
}
int otrazhenie(int a) {
  int res = 0;
  while (a != 0) {
    res = res * 10 + a % 10;
    a /= 10;
  }
  return res;
}
int main() {
  int n;
  cin >> n;
  int sum = 0;
  int x;
  for (int i = 1; i <= n; i++) {
    cin >> x;
    sum += x * i;
  }
  cout << sum;
  return 0;
}
