#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int main(){
   int n , types_i,types[n];
    scanf("%d",&n);
    int b[n];

    for(types_i = 0; types_i < n; types_i++){
       scanf("%d",&types[types_i]);
    }

    for(types_i=0;types_i<n;types_i++){
        b[types_i]=0;
    }
     for(types_i=0;types_i<n;types_i++){
        b[types[types_i]]++;
        if (b[types_i]>1){
        printf ("%d",types_i);
    }


    }


    return 0;
}