#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  long long total = 0;
  for (int i = 1; i <= n; ++i) {
    long long num;
    cin >> num;
    total += ((num - 1) * i) + 1;
  }
  cout << total << '\n';
}
