#include <bits/stdc++.h>
using namespace std;
long long n, m, x, a, b, cnt, ans;
string s1, s2;
set<char> st;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> x;
    a += x * i;
  }
  cout << a << endl;
}
