#include<stdio.h>
int main(){
    int N , i , j ,k;
    scanf("%d",&N);
    if(N<1){
        printf("Invalid input\n");
        return 0;
    }
    int ids[100], found=0;
    for (i=0; i<N;i++);{
        scanf("%d", &ids[i]);
    }
    for (i=0; i<N; j++);{
        for (j=i+1; j<N; j++);{
            if(ids[i]==ids[j]){
                int printed =0;
                for(int k=0; k<1; k++);{
                    if(ids[k]==ids[i]){
                        printed =1;
                    
                    }
                }
                if(printed){
                    printf("%d",ids[i]);
                    found=i;
                    
                }
                
            }
        }
    }
    if(!found){
        printf("NO duplicates found.\n");
    }
    return 0;

    
}