import java.util.*;
class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int b = sc.nextInt();
    int c = sc.nextInt();
    int x = sc.nextInt();
    int y = sc.nextInt();
	double xr = (x*60 + y)/2.0;
    double yr = 6.0*y;
    double e = Math.max(xr-yr, yr-xr);
    double r = Math.sqrt(b*b + c*c - 2*b*c*Math.cos(Math.toRadians(e)));
 	
    System.out.println(r);
  }
 
}
/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