#include <cstdio>
#include <cstring>
#include <cassert>
#include <iostream>
#include <algorithm>
#include <vector>
#include <set>
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR (i, 0, n)
#define _ << " _ " <<
#define TRACE(x) cerr << #x << " = " << x << endl
#define debug(...) fprintf(stderr, __VA_ARGS__)
//#define debug
//#define TRACE(x)
using namespace std;
typedef long long llint;
const int MAXN = 300010;
int n, a[MAXN];
llint sol;
int main(void) {
scanf("%d",&n);
n *= 3;
REP(i, n) scanf("%d",&a[i]);
sort(a, a + n);
int lo = 0, hi = n - 1;
while (lo <= hi) {
sol += a[hi - 1];
++lo;
hi -= 2;
}
cout << sol << endl;
return 0;
}