import java.util.Scanner;

public class Main {

    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        int A = Integer.parseInt(sc.next());
        int B = Integer.parseInt(sc.next());
        int H = Integer.parseInt(sc.next());
        int M = Integer.parseInt(sc.next());

        double x2 = A*A + B*B -2*A*B*(Math.cos(Math.toRadians(30*H+(double)(M/2.0)-6*M)));
        double ans = Math.sqrt(x2);
        
        System.out.println(ans);

        sc.close();
    }
    
}
/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