#include<bits/stdc++.h>
using namespace std;
int main(){
    int n, a[1009],i=0,temp,b[1009],j=0;
    scanf("%d",&n);
    temp=n;
    while(temp--){
        scanf("%d",&a[i]);
        i++;
    }i=0;
    sort(a,a+n);
    while(i<n){
        if(a[i]!=a[i+1]){b[j]=a[i];j++;}
        i++;
    }
    printf("%d\n",j);i=0;
    while(i<j){
        printf("%d ",b[i]);
        i++;
    }
}