import java.io.*;
import java.util.*;

public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static PrintWriter pw = new PrintWriter(System.out);
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	}

	public static void solution(String[] args) throws Exception{

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	}


	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

}
 import java.io.*; io.* java import java.util.*; util.* java public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static PrintWriter pw = new PrintWriter(System.out);
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	}

	public static void solution(String[] args) throws Exception{

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	}


	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

} Main final static long MOD = 1000000007; MOD 1000000007 public static String[] Ws = null; Ws null public static int wsIndx = 0; wsIndx 0 public static BufferedReader in = null; in null public static long cnt=0; cnt 0 public static PrintWriter pw = new PrintWriter(System.out); pw new PrintWriter(System.out) public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	} main {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	} solution(args) solution args if(in!=null){
			in.close();
		} in!=null in null {
			in.close();
		} in.close() in.close in pw.flush() pw.flush pw pw.close() pw.close pw String[] args args public static void solution(String[] args) throws Exception{

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	} solution {

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	} int A = nextInt(); A nextInt() nextInt int B = nextInt(); B nextInt() nextInt int H = nextInt(); H nextInt() nextInt int M = nextInt(); M nextInt() nextInt double x=30*(H%12)+0.5*M; x 30*(H%12)+0.5*M 30*(H%12) 30 (H%12) H 12 0.5*M 0.5 M double y=6*M; y 6*M 6 M double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y))); r Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y))) Math.min Math 1.0*Math.abs(x-y) 1.0 Math.abs(x-y) Math.abs Math x-y x y 1.0*Math.abs(360-Math.abs(x-y)) 1.0 Math.abs(360-Math.abs(x-y)) Math.abs Math 360-Math.abs(x-y) 360 Math.abs(x-y) Math.abs Math x-y x y double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r))); ans Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r))) Math.sqrt Math A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)) A*A+B*B A*A A A B*B B B 2*A*B*Math.cos(Math.toRadians(r)) B 2*A*B*Math.cos(Math.toRadians(r)) 2 A B Math.cos(Math.toRadians(r)) Math.cos Math Math.toRadians(r) Math.toRadians Math r System.out.printf("%.12f\n",ans) System.out.printf System.out System System.out "%.12f\n" ans String[] args args public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	} check {
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	} if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		} in == null in null {
			in = new BufferedReader(new InputStreamReader(System.in));
		} in = new BufferedReader(new InputStreamReader(System.in)) in new BufferedReader(new InputStreamReader(System.in)) if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		} Ws==null || Ws.length<=wsIndx Ws==null Ws null Ws.length<=wsIndx Ws.length Ws Ws.length wsIndx {
			Ws = in.readLine().split(" ");
			wsIndx=0;
		} Ws = in.readLine().split(" ") Ws in.readLine().split(" ") in.readLine().split in.readLine() in.readLine in " " wsIndx=0 wsIndx 0 public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	} nextInt {
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	} check() check return Integer.parseInt(Ws[wsIndx++]); Integer.parseInt(Ws[wsIndx++]) Integer.parseInt Integer Ws[wsIndx++] Ws wsIndx++ wsIndx public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	} nextLong {
		check();
		return Long.parseLong(Ws[wsIndx++]);
	} check() check return Long.parseLong(Ws[wsIndx++]); Long.parseLong(Ws[wsIndx++]) Long.parseLong Long Ws[wsIndx++] Ws wsIndx++ wsIndx public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	} nextString {
		check();
		return Ws[wsIndx++];
	} check() check return Ws[wsIndx++]; Ws[wsIndx++] Ws wsIndx++ wsIndx public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} nextInts {
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} check() check int[] tmp = new int[Ws.length]; tmp new int[Ws.length] Ws.length Ws Ws.length for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		} int i=0; int i=0; i 0 i<tmp.length i tmp.length tmp tmp.length i++ i++ i {
			tmp[i]=Integer.parseInt(Ws[i]);
		} {
			tmp[i]=Integer.parseInt(Ws[i]);
		} tmp[i]=Integer.parseInt(Ws[i]) tmp[i] tmp i Integer.parseInt(Ws[i]) Integer.parseInt Integer Ws[i] Ws i wsIndx=Ws.length wsIndx Ws.length Ws Ws.length return tmp; tmp public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} nextLongs {
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} check() check long[] tmp = new long[Ws.length]; tmp new long[Ws.length] Ws.length Ws Ws.length for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		} int i=0; int i=0; i 0 i<tmp.length i tmp.length tmp tmp.length i++ i++ i {
			tmp[i]=Long.parseLong(Ws[i]);
		} {
			tmp[i]=Long.parseLong(Ws[i]);
		} tmp[i]=Long.parseLong(Ws[i]) tmp[i] tmp i Long.parseLong(Ws[i]) Long.parseLong Long Ws[i] Ws i wsIndx=Ws.length wsIndx Ws.length Ws Ws.length return tmp; tmp public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	} nextStrings {
		check();
		wsIndx=Ws.length;
		return Ws;
	} check() check wsIndx=Ws.length wsIndx Ws.length Ws Ws.length return Ws; Ws public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static PrintWriter pw = new PrintWriter(System.out);
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	}

	public static void solution(String[] args) throws Exception{

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	}


	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

} public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static PrintWriter pw = new PrintWriter(System.out);
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	}

	public static void solution(String[] args) throws Exception{

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	}


	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

} Main
import java.io.*;
import java.util.*;

public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static PrintWriter pw = new PrintWriter(System.out);
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
		pw.flush();
		pw.close();
	}

	public static void solution(String[] args) throws Exception{

		int A = nextInt();
		int B = nextInt();
		int H = nextInt();
		int M = nextInt();


		double x=30*(H%12)+0.5*M;
		double y=6*M;

		//内角の角度
		double r = Math.min(1.0*Math.abs(x-y),1.0*Math.abs(360-Math.abs(x-y)));

		double ans = Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.toRadians(r)));

		System.out.printf("%.12f\n",ans);


	}


	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

}

