import java.util.Scanner;
class Main{
	public static void main(String[] args){
    	Scanner sr = new Scanner(System.in);
      	int A = sr.nextInt();
      	int B = sr.nextInt();
      	int H = sr.nextInt();
      	int M = sr.nextInt();
      	
      double angleA = (H*60+M)*Math.PI/360;    
      double angleB = (M*Math.PI)/30;
      double C = A*A+B*B-(2*A*B*Math.cos(Math.abs(angleA-angleB)));
      System.out.println(Math.sqrt(C));
    }
} 
/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