Kyselyt

import java.util.Scanner;

public class Kyselyt {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int q = input.nextInt();
        for (int i = 0; i < q; i++) {
            int index = input.nextInt();
            if (index < 10) {
                System.out.println(index);
            }
            else {
                int base = 10;
                int len = 1;
                while (true) {
                    if (index < base) {
                        base = base - 90 * len;
                        break;
                    }
                    len = len + 1;
                    base = base + 90 * len;
                }
                System.out.println(Integer.toString((int) Math.pow(10, len - 1) + Math.floorDiv(index - base, len)).charAt((index - (base % len)) % len));
            }
        }
    }
}

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 90
	at java.lang.String.charAt(String.java:658)
	at Kyselyt.main(Kyselyt.java:23)

Test 3

Group: 3

Verdict: RUNTIME ERROR

Exception in thread "main" java.util.InputMismatchException: For input string: "672274832941907421"
	at java.util.Scanner.nextInt(Scanner.java:2123)
	at java.util.Scanner.nextInt(Scanner.java:2076)
	at Kyselyt.main(Kyselyt.java:8)