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