#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <fstream>
#include <stack>
#include <map>
#include <cstring>
#include <cmath>
#include <set>
#include <iterator>
#include <cmath>

using namespace std;



int main() {
    multiset<int> s, s2;
    int a, k = 0, answ = 1;
    cin >> a;
    while(a != 0)
    {
        if(a > 0)
            s.insert(a);
        if (a < 0)
            s2.insert(a);
        cin >> a;
    }
    if (s.size() >= 1 & s2.size() >= 1)
        answ = (*s.rbegin()) * (*s2.begin());
    if (s.size() == 0)
        for(auto i = s2.rbegin(); i != s2.rend(); ++i)
        {
            ++k;
            answ = answ * (*i);
            if (k == 2)
                break;
        }
    if (s2.size() == 0)
        for(auto i:s)
        {
            ++k;
            answ *= i;
            if (k == 2)
                break;
        }
    cout << answ;
}