#include <bits/stdc++.h>
using namespace std;
template <class T>
string toString(T n) {
  ostringstream ost;
  ost << n;
  ost.flush();
  return ost.str();
}
int main(int argc, char *argv[]) {
  int n;
  cin >> n;
  long long r = 0;
  long long t;
  for (int i = (0); i < (n); ++i) {
    cin >> t;
    r += t + (i * (t - 1));
  }
  cout << r << endl;
  return 0;
}
