#if defined(__GNUC__) && !defined(__clang__)

#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;

using ordered_set = tree<int, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>;

using ordered_map = tree<int, int, less<>, rb_tree_tag, tree_order_statistics_node_update>;

struct tree2d {

vector<ordered_set> sets;

tree2d(int n) : sets(n) {}

void add(int x, int v) {

for (; x < sets.size(); x |= x + 1)

sets[x].insert(v);

}

void remove(int x, int v) {

while (x < sets.size()) {

sets[x].erase(v);

x += x & -x;

}

}

int query(int x, int y1, int y2) {

int res = 0;

for (; x >= 0; x = (x & (x + 1)) - 1)

res += sets[x].order_of_key(y2 + 1) - sets[x].order_of_key(y1);

return res;

}

};

// usage example

int main() {

ordered_set set;

ordered_map map;

map.insert(make_pair(1, 2));

set.insert(1);

set.insert(2);

set.insert(4);

set.insert(8);

set.insert(16);

cout << *set.find_by_order(1) << endl; // 2

cout << *set.find_by_order(2) << endl; // 4

cout << *set.find_by_order(4) << endl; // 16

cout << (set.end() == set.find_by_order(6)) << endl; // true

cout << set.order_of_key(-5) << endl; // 0

cout << set.order_of_key(1) << endl; // 0

cout << set.order_of_key(3) << endl; // 2

cout << set.order_of_key(4) << endl; // 2

cout << set.order_of_key(400) << endl; // 5

cout << endl;

tree2d t(10);

t.add(1, 5);

t.add(3, 6);

cout << t.query(3, 5, 6) << endl;

}

#else

int main() {}

#endif