#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  while (cin >> n) {
    int a;
    int ans = 0;
    for (int i = 1; i <= n; i++) {
      cin >> a;
      ans += a * i;
    }
    cout << ans << endl;
  }
  return 0;
}
