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

/**************************************************************
	Problem: 1183
	User: zzz
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/