#include<iostream>
#include<cstdio>
using namespace std;
const int N = 1010;
int n;
int g[N];
int main()
{
    scanf("%d",&n);
    for(int i = 0;i < n;i ++) 
    {
        int res;
        scanf("%d",&res);
        g[res] ++;
    }
    int res = 0;
    for(int i = 0;i <= 1000;i ++)
    {
        if(g[i] != 0)
        {
            res ++;
            g[i] = 1;
        }
    }
    printf("%d\n",res);
    for(int i = 0;i <= 1000;i ++)
        if(g[i] != 0)
          printf("%d ",i);  
    return 0;
}