#include <bits/stdc++.h>
using namespace std;
int main(int argc, char* argv[]) {
  int n;
  cin >> n;
  vector<long long> variants(n);
  for (int i = 0; i < n; ++i) cin >> variants[i];
  long long result = 0;
  for (int i = 0; i < variants.size(); ++i)
    result += variants[i] + i * (variants[i] - 1);
  cout << result << endl;
  return 0;
}
