VOTERS: I get a wrong answer, sample input works fine. Please let me know of any tricky test case I may be missing. Thanks in advance.

general
,
1

import java.util.;
import java.lang.;

class VOTERS{
    public static void main(String[] args){
	Scanner scanner = new Scanner(System.in);
	int N1 = scanner.nextInt();  // number of voters in first list
	int N2 = scanner.nextInt();  //  "     "   "     "  second "
	int N3 = scanner.nextInt();  //  "     "   "     "  third "

	int[] firstList = new int[N1];
	int[] secondList = new int[N2];
	int[] thirdList = new int[N3];
	for(int i=0;i<N1;i++){
	    firstList[i] = scanner.nextInt();
	}
	for(int i=0;i<N2;i++){
	    secondList[i] = scanner.nextInt();
	}
	for(int i=0;i<N3;i++){
	    thirdList[i] = scanner.nextInt();
	}
	HashMap<Integer, Integer> countMap = new HashMap<Integer, Integer>();
	for(int i=0;i<N1;i++){
	    if(countMap.containsKey(firstList[i])){
		countMap.put(firstList[i], countMap.get(firstList[i]) + 1);
	    }
	    else{
		countMap.put(firstList[i], 1);
	    }
	}
	for(int i=0;i<N2;i++){
	    if(countMap.containsKey(secondList[i])){
		countMap.put(secondList[i], countMap.get(secondList[i]) + 1);
	    }
	    else{
		countMap.put(secondList[i], 1);
	    }
	}
	for(int i=0;i<N3;i++){
	    if(countMap.containsKey(thirdList[i])){
		countMap.put(thirdList[i], countMap.get(thirdList[i]) + 1);
	    }
	    else{
		countMap.put(thirdList[i], 1);
	    }
	}
	ArrayList<Integer> result = new ArrayList<Integer>();
	for(Map.Entry<Integer, Integer> entry : countMap.entrySet()){
	    if(entry.getValue() > 1){
		result.add(entry.getKey());
	    }
	}
	System.out.println(result.size());
	for(int i=0;i<result.size();i++){
	    System.out.println(result.get(i));
	}
    }
}