import java.util.*;
import java.math.BigInteger;
public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double pai = Math.PI;
    double a = sc.nextDouble();
    double b = sc.nextDouble();
    double h = sc.nextDouble();
    double m = sc.nextDouble();
    // 時針は分針にも影響されることに注意
    double cosC = Math.cos(Math.abs(30*(h+m/60) - 6*m) / 180 * pai);
    double ansPow = b*b + a*a - 2*a*b*cosC;
    System.out.println(Math.pow(ansPow, 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