import java.util.Scanner;


class Main{
 public static void main(String args[]){
   Scanner sc = new Scanner(System.in);
   int A = sc.nextInt();
   int B = sc.nextInt();
   int C = sc.nextInt();
   int D = sc.nextInt();
   
    double radian = Math.PI*2*(C/12.0 + (D/60.0)/12.0 - D / 60.0);
   
  
   System.out.println(Math.sqrt((double)((A*A)+(B*B)-(2*A*B*Math.cos(radian)))));
 
 }
}

/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