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