#include <stdio.h>

int main(){
    int n, i , j;
    scanf("%d", &n);
    
    if (n < 1){
        printf("invalid input");
        return 0;
    }
    int i[100];
    for (i = 0; i < n; i++){
        scanf ("%d", &id[i]);
    }
    int found = 0;
    for (i = 0; i < n; i++){
        for (j = i+1; j < n; j++){
            if (id[i] == id[j]){
                printf("%d", id[i]);
                found = 1;
                break;
            }
        }
    }
    if (found == 0)
        printf("no duplicates found");
    return 0;
}