Kyselyt

import java.util.Scanner;
import java.math.BigInteger;
public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int num = Integer.parseInt(input.nextLine());
        BigInteger[] kyselyt = new BigInteger[num];
        BigInteger biggest = BigInteger.ZERO;

        for (int i = 0; i < num; i++) {
            kyselyt[i] = new BigInteger(input.nextLine());
            if (kyselyt[i].compareTo(biggest) == 1) {
                biggest = kyselyt[i];
            }
        }

        StringBuilder sb = new StringBuilder();
        BigInteger last = BigInteger.ONE;

        while (BigInteger.valueOf(sb.length()).compareTo(biggest) == -1) {
            sb.append(last);
            last = last.add(BigInteger.ONE);
        }

        String numbers = sb.toString();

        for (BigInteger kysely : kyselyt) {
            System.out.println(numbers.charAt(kysely.intValue()));
        }
    }
}

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...

Test 3

Group: 3

Verdict: TIME LIMIT EXCEEDED