#include<bits/stdc++.h>
using namespace std;
int n,s,m,a[1100],b[1100];
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	sort(a+1,a+1+n);
	a[n+1]=-1;
	s=1;
	for(int i=2;i<=n+1;i++)
	{
		if(a[i]==a[i-1])s++;
		else{
			b[a[i-1]]=s;
			m+=s-1;
			s=1;
		}
	}
	cout<<n-m<<endl;
	for(int i=1;i<=1000;i++)if(b[i]>=1)cout<<i<<" "; 
}