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