//####################################################################
//#####In the Name Of Allah,the Most Gracious,the Most Merciful.######
//####################################################################
//############Created by Sazid Rahman Simanto on 3/20/17.#############
//#####Copyright © 2017 Sazid Rahman Simanto. All rights reserved.####
//####################################################################

#include <iostream>
#include <string>
#include <sstream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <utility>
#include <bitset>
#include <list>
#include <algorithm>
#include <complex>

using namespace std;

#define MSET(a,x) memset(a,x,sizeof a)
#define FOR(i,x,y) for(int i=(x);i<=(y);i++)
#define FORR(i,x,y) for(int i=(x);i<(y);i++)
#define ROF(i,x,y) for(int i=(y);i>=(x);i--)
#define SQ(x) ((x)*(x))
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define ff first
#define ss second
#define pb push_back
#define inf             1061109567
#define maxn            100010
#define esp             1e-8
#define mod             1000000007
#define ll              long long
#define ull             unsigned long long
#define pii             pair<int,int>
#define pll             pair<ll,ll>
#define read()          freopen("input.txt", "r", stdin)
#define write()         freopen("output.txt", "w", stdout)


typedef pair<string, int> ii;
typedef complex<double> base;
const double PI = acos(- 1);
typedef long double ld;

template <class T> inline T bigmod(T a, T b, T M) {
        ll ret = 1;
        for(; b > 0; b >>= 1) {
                if(b & 1) ret = (ret * a) % M;
                a = (a * a) % M;
        }
        return (T)ret;
}

template <class T> inline T gcd(T a,T b){

        while (a && b)a > b ? a %= b : b %= a;
        return a + b;
}


template <class T> inline T lcm(T a, T b) { return (a / gcd(a, b)) * b; }

template <class T> inline T poww(T a, T b) {
        ll ret = 1;
        for(; b > 0; b >>= 1) {
                if(b & 1) ret = ret * a;
                a = a * a;
        }
        return (T)ret;
}

pii exEuclid(int a, int b) {
        if(b == 0) return pii(1, 0);
        else {
                pii r = exEuclid(b, a%b);
                return pii(r.ss, r.ff-r.ss*(a/b));
        }
}

int modInv(int a, int m) { pii ret = exEuclid(a, m); return ((ret.ff % m) + m ) % m; }

int Set(int N, int pos) {return N = N | (1 << pos);}
int reset(int N, int pos) {return N = N & ~ (1 << pos);}
bool check(int N, int pos) {return (bool) (N & (1 << pos));}

//####################################################################
//##################Template Ends Here################################
//####################################################################
ll arr[3 * maxn];

int main() {

        //read();
        //ios_base::sync_with_stdio(false); cin.tie(NULL);cout.tie(NULL);
        //write();
        int n;
        cin >> n;

        FOR(i, 1, 3 * n){
                cin >> arr[i];
        }

        sort(arr + 1, arr  + 1 + 3 * n);

        ll ans = 0;

        FOR(i, n + 1, 3 * n){
                if((i - n) % 2 == 1){
                        ans += arr[i];
                }
        }

        cout << ans << endl;

        return 0;
}


Measured memory_bytes: 2560