#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, a[120], i, sum = 0;
  cin >> n;
  for (i = 0; i < n; i++) cin >> a[i];
  for (i = 0; i < n; i++) sum += a[i] + (a[i] - 1) * i;
  cout << sum << endl;
  return 0;
}
