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