#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<int>, rb_tree_tag,
		tree_order_statistics_node_update> Tree;

int main() {
	Tree X;
	for (int i = 1; i <= 16; i <<= 1) X.insert(i); // {1, 2, 4, 8, 16}
	cout << *X.find_by_order(3) << endl; // => 8
	cout << X.order_of_key(10) << endl; // => 4 = min i, mit X[i] >= 10
	return 0;
}