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