import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        double a = sc.nextDouble();
        double b = sc.nextDouble();
        int h = sc.nextInt();
        int m = sc.nextInt();
        int time = h*60 + m;
        
        double len = 0;
        double rad = 0;
        double hh = 0;
        double mm = 0;

        for(int i=0; i<time; i++) {
            hh += 0.5;
            mm += 6;
        }
        hh = hh % 360;
        mm = mm % 360;
        //System.out.println(hh);
        //System.out.println(mm);
        rad = Math.abs(hh - mm);


        len = Math.sqrt(Math.pow(a,2)+Math.pow(b,2) - 2*a*b* Math.cos(Math.toRadians(rad)));
        System.out.println(len);
    }
}
/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