#include <bits/stdc++.h>
using namespace std;
int main() {
  int p1, p2, p3;
  scanf("%d", &p1);
  p3 = 0;
  for (int i = 1; i <= p1; ++i) {
    scanf("%d", &p2);
    p3 += p2 * i;
  }
  while (scanf("%d", &p2) == 1) {
    while (1)
      ;
  }
  cout << p3 << endl;
  return 0;
}
