#include <bits/stdc++.h>
int asalmi(int x) {
  int i, k = (int)sqrt(x);
  for (i = 2; i <= k; i++)
    if (x % i == 0) return 0;
  return 1;
}
int ters(int x) {
  int bas = 0, t = x, i, k = 0;
  while (x) {
    k *= 10;
    k += x % 10;
    x /= 10;
  }
  return k;
}
using namespace std;
long long m, n;
long long int a[10000];
void read() {
  int i = 10, j, say = 0;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> j;
    m += j * i;
  }
  cout << m;
}
void solve() { int i, j; }
void write() { int i, j; }
int main() {
  read();
  solve();
  write();
  return 0;
}
