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