#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n, sum = 0;
  cin >> n;
  int arr[n];
  for (long long i = 0; i < n; i++) cin >> arr[i];
  for (long long i = 0; i < n; i++) {
    sum += arr[i] + (arr[i] - 1) * i;
  }
  cout << sum << endl;
}
