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 h = sc.nextInt();
    int m = sc.nextInt();
    
    double angH = 30*h;
    double angM = 5.5*m;
    double ang = Math.toRadians(Math.abs(angH - angM));
    double c = 0;
    c = Math.sqrt(a*a + b*b - 2*a*b*Math.cos(ang));
    System.out.print(c);
  }
}

/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