C++ :

#include<bits/stdc++.h>
using namespace std;

int a[1100],n,m;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	set<int> s(a+1,a+n+1);
	set<int>::iterator it;
	for(it=s.begin();it!=s.end();it++) m++;
	cout<<m<<endl;
	for(it=s.begin();it!=s.end();it++) cout<<*it<<" ";
	return 0;
}

Pascal :

var
   a:array[1..1000] of boolean;
   i,j,m,n,x:longint;
begin
  readln(n);
  m:=0;
  for i:=1 to n do
  begin
    read(x);
    a[x]:=true;
  end;
  for i:=1 to 1000 do if a[i]=true then m:=m+1;
  writeln(m);
  for j:=1 to 1000 do if a[j]=true then write(j,' ');
end.

Python :

import math
import sys
n=int(input())
s=list(map(int,input().split()))
s=list(set(s))
s.sort()
print(len(s))
for item in s:
    print(item,end=" ")