#include <bits/stdc++.h>


//_ ************************** Advanced PBDS ***********************************

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<class T>
using ordered_set = tree<
    T,
    null_type,
    less<T>,
    rb_tree_tag,
    tree_order_statistics_node_update
>;


//_ ****************************************************************************


#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************




void solve() {

    ordered_set<int> s;

    for (auto x : {10LL, 5LL, 20LL, 15LL, 8LL, 2LL})
        s.insert(x);

	int n = s.size();

    cout << "Index    : ";
    for (int i=0; i<=n; i++)	cout << i << " ";	cout << endl;
    
    cout << "Elements : ";
    for (auto x : s)	cout << x << " ";	cout << endl;
    cout << endl;



	
    int x = 10;

    cout << "Index of "<< x <<"   : " << s.order_of_key(x) << endl;

    cout << "Count < "<< x <<"    : " << s.order_of_key(x) << endl;
    cout << "Count <= "<< x <<"   : " << s.order_of_key(x+1) << endl;
    cout << "Count > "<< x <<"    : " << n - s.order_of_key(x+1) << endl;
    cout << "Count >= "<< x <<"   : " << n - s.order_of_key(x) << endl;
    
    cout << endl;

    // -------------------------------------------------
    


    cout << "0th Smallest  : " << *s.find_by_order(0) << endl;
    cout << "2nd Smallest  : " << *s.find_by_order(2) << endl;
    cout << "1st Largest   : " << *s.find_by_order(n-1) << endl;
    cout << "2nd Largest   : " << *s.find_by_order(n-2) << endl;

    cout << "Median        : " << *s.find_by_order(n / 2) << endl;

	cout << endl;


    // -------------------------------------------------

    int L = 5, R = 15;

    cout << "Elements in [" << L << "," << R << "] : "
         << s.order_of_key(R + 1) - s.order_of_key(L) << endl << endl;

    // -------------------------------------------------


    cout << "Iterate By Index : ";

    for (int i = 0; i < n; i++)	{
    	cout << *s.find_by_order(i) << " ";
	}
    cout << endl;

    // -------------------------------------------------


    
    
    
}



















int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}