import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	}
} Main public static void main(String[] args) {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	} main {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	} int ans=0; ans 0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = sc.nextInt(); a sc.nextInt() sc.nextInt sc long b = sc.nextInt(); b sc.nextInt() sc.nextInt sc long c = sc.nextInt(); c sc.nextInt() sc.nextInt sc long d = sc.nextInt(); d sc.nextInt() sc.nextInt sc long ac = a*c; ac a*c a c long ad = a*d; ad a*d a d long bc = b*c; bc b*c b c long bd = b*d; bd b*d b d long i = 0; i 0 long j = 0; j 0 if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		} ac > ad ac ad {
			i = ac;
		} i = ac i ac {
			i = ad;
		} i = ad i ad if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		} bc > bd bc bd {
			j = bc;
		} j = bc j bc {
			j = bd;
		} j = bd j bd if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		} i > j i j {
			System.out.println(i);
		} System.out.println(i) System.out.println System.out System System.out i {
			System.out.println(j);
		} System.out.println(j) System.out.println System.out System System.out j String[] args args public class Main {
	public static void main(String[] args) {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	}
} public class Main {
	public static void main(String[] args) {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		int ans=0;
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long c = sc.nextInt();
		long d = sc.nextInt();

		long ac = a*c;
		long ad = a*d;
		long bc = b*c;
		long bd = b*d;

		long i = 0;
		long j = 0;

		if(ac > ad) {
			i = ac;
		}
		else {
			i = ad;
		}

		if(bc > bd) {
			j = bc;
		}
		else {
			j = bd;
		}

		if(i > j) {
			System.out.println(i);
		}
		else {
			System.out.println(j);
		}
	}
}
