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