import java.util.Scanner;
import java.lang.Math;
 
public 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 rad = Math.abs(H*30 + M*0.5 - M*6);
      		if(rad >= 180){
            rad = 360 - rad;
            }
      		double C = 0;
      		
      		C  =  Math.pow(A,2)+Math.pow(B,2) - 2*A*B*Math.cos(Math.toRadians(rad));
      
		System.out.println(Math.pow(C,0.5));
	}
 
}
/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