import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    } main {
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = sc.nextLong(); a sc.nextLong() sc.nextLong sc long b = sc.nextLong(); b sc.nextLong() sc.nextLong sc long c = sc.nextLong(); c sc.nextLong() sc.nextLong sc long d = sc.nextLong(); d sc.nextLong() sc.nextLong sc long resultA = a * c; resultA a * c a c resultA = resultA < a * d ? a * d : resultA resultA resultA < a * d ? a * d : resultA resultA < a * d resultA a * d a d a * d a d resultA long resultB = b * c; resultB b * c b c resultB = resultB < b * d ? b * d : resultB resultB resultB < b * d ? b * d : resultB resultB < b * d resultB b * d b d b * d b d resultB if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        } resultA < resultB resultA resultB {
            System.out.println(resultB);
        } System.out.println(resultB) System.out.println System.out System System.out resultB {
            System.out.println(resultA);
        } System.out.println(resultA) System.out.println System.out System System.out resultA String[] args args public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    }
} public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // xの範囲
        long a = sc.nextLong();
        long b = sc.nextLong();
        // yの範囲
        long c = sc.nextLong();
        long d = sc.nextLong();

        long resultA = a * c;
        resultA = resultA < a * d ? a * d : resultA;
        long resultB = b * c;
        resultB = resultB < b * d ? b * d : resultB;
        if (resultA < resultB) {
            System.out.println(resultB);
        } else {
            System.out.println(resultA);
        }
    }
}
