#include <iostream>
#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<int>,
rb_tree_tag,
tree_order_statistics_node_update>
set_t;
int main()
{
set_t s;
s.insert(12);
s.insert(50);
s.insert(30);
s.insert(20);
cout << "1st element: " << *s.find_by_order(1) << '\n';
cout << "Position of 30: " << s.order_of_key(30) << '\n';
return 0;
}
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