#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, a, ans = 0;
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> a;
    ans += a * i;
  }
  cout << ans;
}
