Policy based data structure

/*
Author: Fuadul Hasan(fuadul202@gmail.com)
BSMRSTU,Gopalganj
*/
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/detail/standard_policies.hpp>
using namespace __gnu_pbds;
using namespace std;


typedef tree<
int,
null_type,
less<int>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;


int solve()
{
	//happy coding

	ordered_set x;
	x.insert(1);
	x.insert(2);
	x.insert(4);
	x.insert(8);
	x.insert(16);

	cout<<*x.find_by_order(1)<<endl;
	cout<<*x.find_by_order(2)<<endl;
	cout<<*x.find_by_order(4)<<endl;
	cout<<*x.find_by_order(8)<<endl;


	cout<<" "<<endl;

	cout<<x.order_of_key(1)<<endl;
	cout<<x.order_of_key(2)<<endl;
	cout<<x.order_of_key(4)<<endl;
	cout<<x.order_of_key(8)<<endl;



	//error()
	return 0;
}

int main(){
	int test = 1, tc = 0;
	//scanf("%d", &test);//(void)getchar();
	while (test--)solve();
	return 0;
}