#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  while (scanf("%d", &n) != EOF) {
    long long ans = 0LL;
    for (int i = 1; i <= n; ++i) {
      int t;
      scanf("%d", &t);
      ans += t * i;
    }
    printf("%I64d\n", ans);
  }
  return 0;
}
