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