Hi, i don't quite understand why I'am getting this error.that says: "Make sure that your solution works with negative numbers like -2000000000

package pl.codegym.task.task05.task0532;

import java.io.*;

/*
Zadanie z algorytmami
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        long maksimum = 0;
        long ilosc = Integer.parseInt(reader.readLine());

        for (int i = 0; i < ilosc;) {
            long a = Integer.parseInt(reader.readLine());
            i++;

            if (maksimum == 0 && a <=0 && i < ilosc) {
                long b = Integer.parseInt(reader.readLine());
                i++;
                maksimum = Math.max(a, b);
            }
            else maksimum = Math.max(maksimum, a);
        }

        System.out.println(maksimum);
    }
}

package pl.codegym.task.task05.task0532;

import java.io.*;

/*
Zadanie z algorytmami
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        int maksimum = 0;
        int ilosc = Integer.parseInt(reader.readLine());


        for (int i = 0; i < ilosc; i++) {
            int a = Integer.parseInt(reader.readLine());
            if (a<0 && maksimum == 0) {
                int b = Integer.parseInt(reader.readLine());
                maksimum = a > b ? a:b;
                i++;
            }
            else maksimum = maksimum > a ? maksimum : a;
        }

        //tutaj wpisz swój kod


        System.out.println(maksimum);
    }
}

package pl.codegym.task.task05.task0532;

import java.io.*;

/*
Zadanie z algorytmami
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        int maksimum = 0;
        int ilosc = Integer.parseInt(reader.readLine());

        for (int i = 0; i < ilosc; i++) {
            int a = Integer.parseInt(reader.readLine());

            if (maksimum == 0 && a < 0) {
                int b = Integer.parseInt(reader.readLine());
                i++;
                maksimum = Math.max(a, b);
            }
            else maksimum = Math.max(maksimum, a);
        }

        System.out.println(maksimum);
    }
}

package pl.codegym.task.task05.task0532;

import java.io.*;

/*
Zadanie z algorytmami
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        long maksimum = 0;
        long ilosc = Integer.parseInt(reader.readLine());

        for (int i = 0; i < ilosc;) {
            long a = Integer.parseInt(reader.readLine());
            i++;

            if (maksimum == 0 && a <=0 && i < ilosc) {
                long b = Integer.parseInt(reader.readLine());
                i++;
                maksimum = Math.max(a, b);
            }
            else maksimum = Math.max(maksimum, a);
        }

        System.out.println(maksimum);
    }
}

package pl.codegym.task.task05.task0532;

import java.io.*;

/*
Zadanie z algorytmami
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        int ilosc =Integer.parseInt(reader.readLine());
        int maksimum = 0;


        for (int i = 0; i < ilosc; i++){
            int a = Integer.parseInt(reader.readLine());

            if (i == 0) maksimum = a;
            else if (a >= maksimum) maksimum = a;
        }
        System.out.println(maksimum);
    }
}