#include <bits/stdc++.h>
using namespace std;
// this repeats the entry in set, dont know how to overcome this???
struct f{
bool operator()( int a, int b){
return a<b;
}
};
int main() {
set<int,f> s;
s.insert(2);
s.insert(1);
s.insert(3);
s.insert(2);
cout<<s.size()<<"\n";
for(auto x: s) cout<<x<<" ";
}
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