fn kaprekarNumbers(p: i32, q: i32) {
    let mut results: Vec<String> = Vec::new();
    for n in p..=q {
        let square = (n as u128).pow(2).to_string();
        let middle = square.len() - n.to_string().len();

        let (left, right) = square.split_at(middle);
        let left_int = left.parse::<i32>().unwrap_or(0);
        let right_int = right.parse::<i32>().unwrap_or(0);
        if left_int + right_int == n {
            results.push(n.to_string());
        }
    }
    if results.len() > 0 {
        println!("{}", results.join(" "))
    } else {
        println!("INVALID RANGE")
    };
}