#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,i,j=0,m=0;
    cin>>n;
    int h[100];
    for(i=0;i<n;i++){
        cin>>h[i];
    } 
    for(i=1;i<=n-1;i++){
        for(j=1;j<=n-i;j++){
            if(h[j-1]>h[j]){
                swap(h[j-1],h[j]);
            }
        }
    }
    for(i=0;i<n;i++){
        if(h[i]!=h[i-1]){
            m++;
        }
    }
    cout<<m<<endl;
    for(i=0;i<n;i++){
        if(h[i]!=h[i-1]){
            cout<<h[i]<<endl;
        }
    }
  
}
/**************************************************************
	Problem: 1183
	User: linzihang
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/