#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	int a[105];
	int t[1005]={0};
	cin>>n;
	int k=0;
	int x;
	for(int i=0;i<n;i++)
	{
		cin>>x;
		if(t[x]==0)
		{
			t[x]=1;
			a[k]=x;
			k++;
		}
	}
	for(int i=1;i<=k-1;i++)
	{
		for(int j=0;j<=k-1-i;j++)
		{
			if(a[j]>a[j+1])
			{
				swap(a[j],a[j+1]);
			}
		}
	}
	cout<<k<<endl;
	for(int i=0;i<k;i++)
	{
		cout<<a[i]<<endl;
	}
	return 0;
}
/**************************************************************
	Problem: 1183
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:25 ms
	Memory:2072 kb
****************************************************************/