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