#include<iostream>
#include<string.h>
using namespace std;
const int Msize=1001;
bool a[Msize];
int b[101];
int main(){
	int N;
	int num;
	scanf("%d",&N);
	int n=N;
	int count=0;
	memset(a,0,sizeof a);
	while(N-->0){
		scanf("%d",&num);
		a[num]=true;
	}
	for(int i=1;i<Msize;i++){
		if(a[i])b[count++]=i;
	}
	printf("%d\n",count);
	for(int i=1;i<count;i++){
		printf("%d ",b[i]);
	}
	return 0;
}