#include<iostream>
#include<cstdio>
using namespace std;
int main(){
	int N,temp;
	scanf("%d",&N);
	int arr[N];
	int t = N;
	for(int i = 0;i<N;i++){
		scanf("%d",&arr[i]);
	}
	for(int i = N;i>1;i--){
		for(int j = 0;j<i-1;j++){
			if(arr[j]>arr[j+1]){
				temp = arr[j];
				arr[j] = arr[j+1];
				arr[j+1]  = temp;
			}
		}
	}
	for(int i = 0;i<N-1;i++){
		if(arr[i]==arr[i+1]){
			arr[i+1] = 0;
			t--;
		}
	}
	printf("%d\n",t);
	for(int i = 0;i<N;i++){
		if(arr[i]!=0){
			printf("%d ",arr[i]);
		}
	}
	return 0;
}