#include <bits/stdc++.h>
using namespace std;
const int N = 2123456;
void fileIO() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
}
int main() {
  long long s = 0, n, x;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x;
    s += x * (i + 1);
  }
  cout << s << endl;
  return 0;
}
