#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,i,x,j,k=0;
	int a[100]={0},f[1001]={0};
	cin>>n;
	for(i=1;i<=n;i++){
		cin>>x;
		if(f[x]==0){
		f[x]=1;
		a[k]=x;
		k++;
		}
	}
	for(i=1;i<=k;i++){
		for(j=1;j<=k-i;j++){
			if(a[j-1]>a[j])
				swap(a[j-1],a[j]);}}
	cout<<k<<endl;
	for(i=1;i<=k;i++)
		cout<<a[i-1]<<endl;
	
	return 0;
	}

/**************************************************************
	Problem: 1183
	User: fzy001
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/