#include <bits/stdc++.h>
using namespace std;
int n;
int sum = 0, d;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &d);
    sum += d * i;
  }
  printf("%d\n", sum);
  return 0;
}
