#include <bits/stdc++.h>
int main() {
  unsigned long n, i, a[10000], s = 0;
  scanf("%ld", &n);
  for (i = 0; i < n; i++) scanf("%ld", &a[i]);
  for (i = 0; i < n; i++) s += a[i] * (i + 1);
  printf("%ld\n", s);
  return 0;
}
