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