#include <bits/stdc++.h>
using namespace std;
int read() {
  int tmp = 0;
  char ch = 0;
  while (ch < '0' || ch > '9') ch = getchar();
  while (ch >= '0' && ch <= '9') tmp = tmp * 10 + ch - '0', ch = getchar();
  return tmp;
}
int main() {
  int n = read(), x, ans = 0;
  for (int i = 1; i <= n; i++) x = read(), ans += i * x;
  printf("%d\n", ans);
  return 0;
}
