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