#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,i,x,m=0,j;
	cin>>n;
	bool f[1001]={0};
	for(i=0;i<n;i++){
		cin>>x;
		if(f[x]==0){
			f[x]=1;
			m++;
		}
	}
	cout<<m<<endl;
	for(i=0;i<1001;i++){
		if(f[i]==1)
		cout<<i<<endl;
	}	 
	return 0;
}
/**************************************************************
	Problem: 1183
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/