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