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