#include <bits/stdc++.h>
using namespace std;
const int N = 1e2 + 5;
int a, b, ans;
inline int read() {
  char c = getchar();
  int x = 0, f = 1;
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -1;
  for (; isdigit(c); c = getchar()) x = x * 10 + c - 48;
  return x * f;
}
int main() {
  a = read();
  for (register int i = 1; i <= a; ++i) {
    b = read();
    ans += i * b;
  }
  cout << ans;
  return 0;
}
