#include<stdio.h>
#include<stdbool.h>
int main(){
    int N;
    scanf("%d", &N);
    if(N < 1){
        printf("Invalid input\n");
        return 0;
    }
    int ids;
    for(int i = 0; i < N; i++){
        scanf("%d", &ids[i]);
    }
    bool seen[2001] = {false};
    bool printed_duplicates = false;
    for(int i = 0; i < N; i++){
        int index = &ids[i] + 1000;
        if(seen[index]){
            if(!printed_duplicates){
                printf("%d", &ids[i]);
                printed_duplicates = true;
            }else {
                printf(" %d", &ids[i]);
            }
        }
        seen[index] = true;
    }
    if(!printed_duplicates){
        printf("No duplicates found\n");
    }
    printf("\n");
    return 0;
}