#include <bits/stdc++.h>
using namespace std;
int main(int argc, char* argv[]) {
  int64_t N, full_sum{0};
  cin >> N;
  for (int i = 1; i <= N; ++i) {
    int64_t a;
    cin >> a;
    full_sum += ((a - 1) * i + 1);
  }
  cout << full_sum;
}
