#include <bits/stdc++.h>
using namespace std;
int main() {
  const int N = 110;
  long long a[N], res = 0;
  int n, i;
  cin >> n;
  for (i = 0; i < n; ++i) {
    cin >> a[i];
    res += -i + a[i] * (i + 1);
  }
  cout << res << endl;
  return 0;
}
