#include<stdio.h>
int main(){
    int N;
    scanf("%d",&N);
    if(N<1){
    printf("Invalid input\n");
    return 0;
}  
    int duplicates[MAX_PARTICIPANTS];
    int duplicatescount =0;
    for(int i=0;i<N;i++){
       int id;
       scanf("%d",&id);
       if(ids[id + 1000]>1 && ids[id + 1000]<=2){
       duplicates[duplicatecount++]=id;
    }
}
if(duplicatecount==0){
    printf("No duplicates found\n");
}else{
    for(int i = 0;i< duplicatescount;i++){
        printf("%d",duplicates[i]);
    }
    printf("\n");
 }
 return 0;
}