ordered_set_PBDS.cpp

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;

// Use pair<int,int> to support multiset like features
typedef tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag,
             tree_order_statistics_node_update>
    oset;

oset curr;

/*
1. Number of elements strictly greater than a[i]
int cnt = sz(curr) - (int)curr.order_of_key({a[i]+1,0});

2. Number of elements strictly less than a[i]
int cnt = (int)curr.order_of_key({a[i],i});

3. Use insert like this : curr.insert({a[id], id});

4. Erasing : curr.erase({a[i], i});
*/

NOTE : long long doesn't work with this.