#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>  
#include <ext/pb_ds/tree_policy.hpp>   
 
using namespace std ;
using namespace __gnu_pbds;
 
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
 
signed main(){
  ordered_set s ;
  s.insert(0) ;
  s.insert(0) ;
  s.insert(0) ; 
  s.insert(0) ;
  cout << int(s.size()) << endl ;
  s.erase(s.find(0)) ;
  cout << int(s.size()) << endl ;
 
}

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