import java.util.*;

public class Main {
	public static void main(String[] args) {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args) {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	}
} Main public static void main(String[] args) {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	} main {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	} 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 out = 0; out 0 if(ac > ad) out = ac;
		else out = ad; ac > ad ac ad out = ac out ac out = ad out ad if(out < bc) out = bc; out < bc out bc out = bc out bc if(out < bd) out = bd; out < bd out bd out = bd out bd System.out.println(out) System.out.println System.out System System.out out sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	}
} Main
import java.util.*;

public class Main {
	public static void main(String[] args) {
		//ABC081A
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		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 out = 0;

		if(ac > ad) out = ac;
		else out = ad;
		if(out < bc) out = bc;
		if(out < bd) out = bd;
		
		// 出力
		System.out.println(out);

		sc.close();
	}
}
