#include<bits/stdc++.h>
using namespace std;
int n,j,i,h,a[105],b[105];
int main(){
    cin>>n;
    for(i=0;i<n;i++){
    	cin>>a[i];
    }
    for(i=0;i<n;i++){
    		for(j=0;j<=i;j++){
    			if(a[i]==b[j]){
    				break;
    			}else if(b[j]==0){
    				b[j]=a[i];
    				h++;
    				break;
    			}
    		}
    	}
    for(i=1;i<h;i++){
    	for(j=0;j<h-i;j++){
    		if(b[j]>b[j+1]){
    			swap(b[j],b[j+1]);
    		}
    		
    	}
    }
    cout<<h<<endl;
    for(i=0;i<h;i++){
    	cout<<b[i]<<endl;
    }
}
/**************************************************************
	Problem: 1183
	User: yangjunwen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/