            import java.util.*;
            class Main{
              public static void main(String[] args){
                Scanner sc = new Scanner(System.in);
                long a = sc.nextLong();
                long b = sc.nextLong();
                long c = sc.nextLong();
                long d = sc.nextLong();
                
                long x = a * c;
                long y = a * d;
                long z = b * c;
                long w = b * d;
                long[] aa = new long[4];
                
                aa[0] = x;
                aa[1] = y;
                aa[2] = z;
                aa[3] = w;
                long max = x;
             
                for(int i = 0; i < 4; i++){
                  if(aa[i] > max){
                    max = aa[i];
                  }
                }
                System.out.println(max);
              }
            }
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz