import java.util.Scanner;
import java.math.*;
 
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();
        sc.close();
 
        //短針と長針のなす角（度数）
        double degree = (30*h + 0.5*m) - 6*m;
 
        double distance = Math.sqrt(a*a + b*b -2*a*b*Math.cos(Math.toRadians(degree)));
 
        System.out.println(distance);
    }    
}
/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