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