import java.util.*;
import java.io.*;
public class Main {
	public static void main(String[] args) throws IOException{
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	}
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
	public static void main(String[] args) throws IOException{
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	}
} Main public static void main(String[] args) throws IOException{
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	} main {
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int[] arr=new int[4]; arr new int[4] 4 for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    } int i=0; int i=0; i 0 i<4 i 4 i++ i++ i {
	    	arr[i]=sc.nextInt();
	    } {
	    	arr[i]=sc.nextInt();
	    } arr[i]=sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc long val1=arr[0]*1l*arr[2]; val1 arr[0]*1l*arr[2] arr[0]*1l*arr[2] arr[0] arr 0 1l arr[2] arr 2 long val2=arr[0]*1l*arr[3]; val2 arr[0]*1l*arr[3] arr[0]*1l*arr[3] arr[0] arr 0 1l arr[3] arr 3 long val3=arr[1]*1l*arr[2]; val3 arr[1]*1l*arr[2] arr[1]*1l*arr[2] arr[1] arr 1 1l arr[2] arr 2 long val4=arr[1]*1l*arr[3]; val4 arr[1]*1l*arr[3] arr[1]*1l*arr[3] arr[1] arr 1 1l arr[3] arr 3 System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4))) System.out.println System.out System System.out Math.max(Math.max(val1, val2), Math.max(val3, val4)) Math.max Math Math.max(val1, val2) Math.max Math val1 val2 Math.max(val3, val4) Math.max Math val3 val4 String[] args args public class Main {
	public static void main(String[] args) throws IOException{
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	}
} public class Main {
	public static void main(String[] args) throws IOException{
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	}
} Main
import java.util.*;
import java.io.*;
public class Main {
	public static void main(String[] args) throws IOException{
	    Scanner sc=new Scanner(System.in);
	    int[] arr=new int[4];
	    for(int i=0;i<4;i++) {
	    	arr[i]=sc.nextInt();
	    }
		long val1=arr[0]*1l*arr[2];
		long val2=arr[0]*1l*arr[3];
		long val3=arr[1]*1l*arr[2];
		long val4=arr[1]*1l*arr[3];
		System.out.println(Math.max(Math.max(val1, val2), Math.max(val3, val4)));
	}
}