another easy problem
#include<iostream>
using namespace std;
int main()
{
int n;
int num[1001]={0},k;
int result=0;
int i;
cin>>n;
for(i=1;i<=n;i++)
{
cin>>k;
if(num[k]==0) result++;
num[k]++;
}
cout<<result<<endl;
for(i=1;i<=1000;i++)
if(num[i]) cout<<i<<" ";
cout<<endl;
return 0;
}
