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