AC

#include <iostream>
#include <cmath>
using namespace std;
int hs[100010];
int main()
{
int n;
int a[110];
cin>>n;
int maxn=-1;
for (int i=1;i<=n;i++)
{
cin>>a[i];
hs[a[i]];
maxn=max(a[i],maxn);
}
int m=0;
for (int i=1;i<=maxn;i)
{
if (hs[i]>=1)
m++;
}
cout<<m<<endl;
for (int i=1;i<=maxn;i++)
{
if (hs[i]>=1)
cout<<i<<' ';
}
return 0;
}