public static void main(String[] args) { /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */ Scanner sc = new Scanner(System.in); ArrayList> list = new ArrayList<>(); int n = sc.nextInt();

    for (int i = 0; i < n; i++) {
        int m = sc.nextInt();
        ArrayList<Integer> a = new ArrayList<Integer>();
        for (int j = 0; j < m; j++) {
            a.add(sc.nextInt());
        }
        list.add(a);
    }

    int x = sc.nextInt();

    for (int i = 0; i < x; i++) {
        int num1 = sc.nextInt()-1;
        int num2 = sc.nextInt()-1;

        if(num1<list.size() && num1>=0) {
            if(num2<list.get(num1).size() && num2>=0) {
                System.out.println(list.get(num1).get(num2));
            }else{
            System.out.println("ERROR!");   
        }
        }
    }

}

Isnt it kinda weird that the author seem to mean index 0 in their queries but uses "1" instead, e.g., for query 1 3 we actually mean the first list (1). It means that we need to shift the index so that when we assign int x to the value, it should be x = value -1 (and int y = value -1).

Its not wrong, it just felt like adding an unneccesary layer of complexity. Perhaps its part of the exercise, i could also misunderstand the reasoning behind it.

The solution, as i see it is to shift the lists in both images and in the tests, so images show lists 0, 1, 2, 3 ,4 ... instead of 1,2,3,4,,, and so the test doesnt expect the list in place 1 but rather in place 0

public static void main(String[] args) {
   Scanner sc = new Scanner(System.in);        
    int n = sc.nextInt();  
    ArrayList<Integer>[] arr = new ArrayList[n];

    for (int i = 0; i < n; i++) {
        int m = sc.nextInt();  
        arr[i] = new ArrayList<>();

        for (int j = 0; j < m; j++) {
            int value = sc.nextInt();
            arr[i].add(value);
        }
    }

    int mn = sc.nextInt();  

    for (int i = 0; i < mn; i++) {
        int val1 = sc.nextInt()-1;  
        int val2 = sc.nextInt()-1;  

        if (val1 < 0 || val1 >= n || val2 < 0 || val2 >= arr[val1].size()) {
            System.out.println("ERROR!");
        } else {
            System.out.println(arr[val1].get(val2));
        }
    }

}

import java.io.; import java.util.; import java.util.Scanner; public class Solution {

public static void main(String[] args) {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
    // you need to answer a few queries
    Scanner sc = new Scanner(System.in);
    ArrayList[] al = new ArrayList[20000]; // including 2000 elements
    int lists = sc.nextInt();

    // read numbers;
    for (int i = 0; i < lists; i++) {
      al[i] = new ArrayList(); // 
      int number = sc.nextInt();
      for(int j = 0; j < number; j++) {
        int value = sc.nextInt();
        al[i].add(value);
      }
    }
    // testing the queries;
    int queries = sc.nextInt();
    for (int i = 0; i < queries; i++) {
      int x = sc.nextInt();
      int y = sc.nextInt();
      try {
        System.out.println(al[x-1].get(y-1));
      } catch (Exception e) {
        System.out.println("ERROR!");
      }
    }
}

}

import java.io.; import java.util.;

public class Solution {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int cantListas = sc.nextInt();
    ArrayList<ArrayList<Integer>> listas = new ArrayList<>();

    for (int i = 0; i < cantListas; i++) {
        int posiciones = sc.nextInt();

        ArrayList<Integer> numeros = new ArrayList<>();

        for (int j = 0; j < posiciones; j++) {
            numeros.add(sc.nextInt());
        }

        listas.add(numeros);
    }

    int cantQueries = sc.nextInt();
    for (int i = 0; i < cantQueries; i++) {
        int lista = sc.nextInt()-1;
        int posicion = sc.nextInt()-1;

        if (listas.get(lista).size() > posicion ) {
            System.out.println(listas.get(lista).get(posicion));
        } else {
            System.out.println("ERROR!");
        }
    }        


    sc.close();
}

}