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