https://www.luogu.com.cn/problem/P1059
#include<cstring>
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<set>
using namespace std;
int a[101];
set<int>st;
int main(void)
{
int n; cin>>n;
int i;
int number=0;
for(int i=0;i<n;i++)
{
cin>>a[i];
st.insert(a[i]);
}
cout<<st.size()<<endl;
for(set<int>::iterator it=st.begin();it!=st.end();it++)
{
cout<<*it<<" ";
}
cout<<endl;
return 0;
}