#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  long long a, ret;
  while (cin >> n) {
    cin >> ret;
    for (int i = 1; i < n; ++i) {
      cin >> a;
      ret += (a - 1) * (i + 1) + 1;
    }
    cout << ret << endl;
  }
  return 0;
}
