#include<stdio.h>
int main()
{
	int n;
	scanf("%d",&n);
	int arr1[n];
	int arr2[1000] = {0};
	int i = 0;
	while(i<n)
	{
		scanf("%d",&arr1[i]);
		i++;
	}
	for(i=0;i<n;i++)
	{
		arr2[arr1[i]]=arr2[arr1[i]]+1;
	}
	
	for(i=0;i<1000;i++)
	{
		if(arr2[i]>0&&arr2[i]!=1)
		{
			n-=1;
		}
	}
	printf("%d\n",n);
	for(i=0;i<1000;i++)
	{
		if(arr2[i]>0)
		{
			printf("%d ",i);
		}
	}
	return 0;
}