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