using namespace std;
#define ll long long
ll sum = 0;
ll a[3 * 123456];
bool (ll x, ll y)
{
   return x > y;
}
int n;
inline void _read(int &x)
{
   x = 0;
   char t = getchar();
 while (!isdigit(t)) t = getchar();
    while (isdigit(t))
    {
        x = x * 10 + t - '0';
        t = getchar();
   }
}
inline void _read(ll &x)
{
   x = 0;
   char t = getchar();
 while (!isdigit(t)) t = getchar();
    while (isdigit(t))
    {
        x = x * 10 + t - '0';
        t = getchar();
   }
}
int main()
{
 _read(n);
    for (int i = 1; i <= 3 * n; i++) _read(a[i]);
   int i = 2;
  sort(a + 1, a + 1 + 3 * n, cmd);
 while (n--)
 {
        sum += a[i];
     i += 2;
  }
    printf("%lld", sum);
   return 0;
}