void kaprekarNumbers(int p, int q) {
    bool found_some {false};
    
    for (int i=p; i<=q; i++){
        string square = to_string(static_cast<long>(i) * i);
        int length_square = square.length();
        int length_number = to_string(i).length();
        
        int first_half = (length_square > 1) ? stoi(square.substr(0, length_square-length_number)) : 0;
        int second_half = stoi(square.substr(length_square-length_number));
        
        if (first_half + second_half == i) {
            cout << i << " ";
            found_some = true;
        }
    }
    
    if (!found_some) cout << "INVALID RANGE";
}