#include <bits/stdc++.h>
using namespace std;
int main() {
  ios ::sync_with_stdio(0);
  cin.tie(0);
  cout << (fixed) << setprecision(9);
  long long n;
  while (cin >> n) {
    long long res = 0;
    for (long long i = (1), _b = (n); i <= _b; ++i) {
      long long a;
      cin >> a;
      res += i * a;
    }
    cout << res << endl;
  }
}
