#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector<int> a;
    int n;

    while (cin >> n)
    {
        if (n == 0)
            break;

        if (n > 0)
        {
            a.push_back(n);
        }
        else if (n == -1)
        {
            int siz = a.size();

            for (int i = 0; i < siz - 1; i++)
            {
                int mini = i;

                for (int j = i + 1; j < siz; j++)
                {
                    if (a[j] < a[mini])
                        mini = j;
                }
                int temp = a[i];
                a[i] = a[mini];
                a[mini] = temp;
            }
            int mid = (siz - 1) / 2;
            cout << a[mid] << endl;
            for (int i = mid; i < siz - 1; i++)
            {
                a[i] = a[i + 1];

            }

            a.pop_back();
        }
    }

    return 0;
}