import java.util.*;
public class Duplicates {
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[] arr=new int[n];
        boolean invalid=false;
        for (int i=0;i<n;i++){
            arr[i]=sc.nextInt();
            if(arr[i]<0){
                invalid=true;
        }
    }
    if(Invalied){
        System.out.println("Invalid input");
        return;
    }

    HashSet<Integer> seen=new HashSet<>();
    LinkedHashSet<Integer> duplicates=new LinkedHashSet<>();
    for(int num:arr){
        if(seen.contains(num)){
            duplicates.add(num);
        }else{
            seen.add(num);
        }
    }
    if(duplicates.isEmpty()){
        System.out.println("No duplicates found");
    }else{
        for(int d:duplicates){
            System.out.println(d);
        }
    }
}
}