#include <bits/stdc++.h>
using namespace std;
const int INF = 1 << 30;
const int maxn = 107;
int n, sum = 0, a, k;
int main() {
  scanf("%d", &n);
  k = 1;
  while (scanf("%d", &a) != EOF) {
    sum += k * a;
    k++;
  }
  printf("%d\n", sum);
  return 0;
}
