#include<iostream>
#include<cstdio>
#include<algorithm> 
using namespace std;
int a[100]={0};
int main(){
	freopen("random.in","r",stdin);  
	freopen("random.out","w",stdout);
    int n;
    scanf("%d",&n);
    int time=0;
    for(int i=1;i<=n;i++){
    	scanf("%d",&a[i]);
    }sort(a+1,a+1+n);
    for(int w=1;w<=n;w++){
    	if(a[w]==a[w+1]){
    		a[w+1]=0;
    	}
    }
    
    sort(a+1,a+1+n);
    for(int t=1;t<=n;t++){
    	if(a[t]>0){
    		time++;
    	}
    }cout<<time<<endl;
    for(int o=1;o<=n;o++){
    	if(a[o]>0){
    		printf("%d ",a[o]);
    	}
    }
	return 0;
}