C :

#include "stdio.h"

int arr[10000];
int n, ans;


void start()
{
	int i;
	ans = 0;
	for (i = 0; i <= 1000; i++)
		arr[i] = 0;
	
}

void main()
{
	int i,x;
	while (scanf("%d", &n) != EOF)
	{
		start();
		for (i = 1; i <= n; i++)
		{
			scanf("%d", &x);
			if (arr[x] == 0)
			{
				arr[x] = 1;
				ans++;
			}
		}
		printf("%d\n", ans);
		for (i = 1; i <= 1000; i++)
		{
			if (arr[i] > 0) printf("%d ", i);
		}
		printf("\n");
	}
	

}

C++ :

#include<stdio.h>
int main()
{
	int a,b,c[1001]={0};
	scanf("%d",&a);
	for (int x=0;x<a;x++)
	{
		scanf("%d",&b);
		c[b]++;
	}
	int akk=0;
	int sum=0;
	for (int y=0;y<1001;y++)
		if (c[y]!=0) 
			sum++;
	printf("%d\n",sum);
	for (int y=0;y<1001;y++)
		if (c[y]!=0) 
		{
			if (akk==1) printf(" ");
			else akk=1;
			printf("%d",y);
		}
		return 0;
}

Pascal :

var
  n,x,i,s:integer;
  a,b:array[1..1000]of integer;
begin
	readln(n);
	for i:=1 to n do begin
		read(x);
		a[x]:=1;
	end;
	s:=0;
	for i:=1 to 1000 do s:=s+a[i];
	writeln(s);
	x:=0;
	for i:=1 to 1000 do
		if a[i]>0 then begin inc(x);b[x]:=i; end;
	for i:=1 to s-1 do write(b[i],' ');write(b[s]);
end.