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