

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.MathContext;
import java.util.StringTokenizer;

public class Main {

	static long expo(long base, long exp) {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	}

	static int calcAngle(int h, int m) {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	}

	public static void main(String args[]) throws Exception {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	}

	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.math.BigDecimal; BigDecimal java.math import java.math.MathContext; MathContext java.math import java.util.StringTokenizer; StringTokenizer java.util public class Main {

	static long expo(long base, long exp) {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	}

	static int calcAngle(int h, int m) {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	}

	public static void main(String args[]) throws Exception {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	}

	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}
} Main static long expo(long base, long exp) {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	} expo {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	} long t = 1L; t 1L while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		} exp > 0 exp 0 {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		} if (exp % 2 != 0)
				t = (t * base); exp % 2 != 0 exp % 2 exp 2 0 t = (t * base) t (t * base) t base base = (base * base) base (base * base) base base exp /= 2 exp 2 return t; t long base base long exp exp static int calcAngle(int h, int m) {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	} calcAngle {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	} int hour_angle = (int) (0.5 * (h * 60 + m)); hour_angle (int) (0.5 * (h * 60 + m)) 0.5 (h * 60 + m) h * 60 h 60 m int minute_angle = (int) (6 * m); minute_angle (int) (6 * m) 6 m int angle = Math.abs(hour_angle - minute_angle); angle Math.abs(hour_angle - minute_angle) Math.abs Math hour_angle - minute_angle hour_angle minute_angle angle = Math.min(360 - angle, angle) angle Math.min(360 - angle, angle) Math.min Math 360 - angle 360 angle angle return angle; angle int h h int m m public static void main(String args[]) throws Exception {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	} main {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	} MyScanner sc = new MyScanner(); sc new MyScanner() int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc int h = sc.nextInt(); h sc.nextInt() sc.nextInt sc int m = sc.nextInt(); m sc.nextInt() sc.nextInt sc double ans = 0.0; ans 0.0 double pi = 3.14159265358979323846264338327950; pi 3.14159265358979323846264338327950 double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0); rad pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0) pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0) pi 2 ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0) (double)h / 12.0 + ((double)m / 60.0) / 12.0 (double)h / 12.0 (double)h 12.0 ((double)m / 60.0) / 12.0 ((double)m / 60.0) (double)m 60.0 12.0 (double)m / 60.0 (double)m 60.0 ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad)) ans (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad)) (double)((long)(a * a) + (long)(b * b)) (long)(a * a) a a (long)(b * b) b b (double)((2.0 * a * b) * Math.cos(rad)) (2.0 * a * b) 2.0 * a * b 2.0 a b Math.cos(rad) Math.cos Math rad System.out.println(Math.sqrt(ans)) System.out.println System.out System System.out Math.sqrt(ans) Math.sqrt Math ans String args[] args public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	} MyScanner BufferedReader br; br StringTokenizer st; st public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		} MyScanner {
			br = new BufferedReader(new InputStreamReader(System.in));
		} br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		} next {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		} while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			} st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			} try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				} catch (IOException e) {
					e.printStackTrace();
				} IOException e {
					e.printStackTrace();
				} e.printStackTrace() e.printStackTrace e {
					st = new StringTokenizer(br.readLine());
				} st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() {
			return Integer.parseInt(next());
		} nextInt {
			return Integer.parseInt(next());
		} return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong() {
			return Long.parseLong(next());
		} nextLong {
			return Long.parseLong(next());
		} return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() {
			return Double.parseDouble(next());
		} nextDouble {
			return Double.parseDouble(next());
		} return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		} nextLine {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		} String str = ""; str "" try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			} catch (IOException e) {
				e.printStackTrace();
			} IOException e {
				e.printStackTrace();
			} e.printStackTrace() e.printStackTrace e {
				str = br.readLine();
			} str = br.readLine() str br.readLine() br.readLine br return str; str public class Main {

	static long expo(long base, long exp) {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	}

	static int calcAngle(int h, int m) {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	}

	public static void main(String args[]) throws Exception {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	}

	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}
} public class Main {

	static long expo(long base, long exp) {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	}

	static int calcAngle(int h, int m) {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	}

	public static void main(String args[]) throws Exception {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	}

	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}
} Main


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.MathContext;
import java.util.StringTokenizer;

public class Main {

	static long expo(long base, long exp) {
		long t = 1L;
		while (exp > 0) {
			if (exp % 2 != 0)
				t = (t * base);

			base = (base * base);
			exp /= 2;
		}
		return t;
	}

	static int calcAngle(int h, int m) {

		int hour_angle = (int) (0.5 * (h * 60 + m));
		int minute_angle = (int) (6 * m);

		int angle = Math.abs(hour_angle - minute_angle);

		angle = Math.min(360 - angle, angle);

		return angle;
	}

	public static void main(String args[]) throws Exception {
		MyScanner sc = new MyScanner();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double ans = 0.0;
		double pi = 3.14159265358979323846264338327950;
		//int angle = calcAngle(h, m);
		
		double rad = pi * 2 * ((double)h / 12.0 + ((double)m / 60.0) / 12.0 - (double)m / 60.0);
		
		
		ans = (double)((long)(a * a) + (long)(b * b)) - (double)((2.0 * a * b) * Math.cos(rad));
		/*BigDecimal br = new BigDecimal(Double.toString(ans));
		br = br.sqrt(new MathContext(20));*/
		System.out.println(Math.sqrt(ans));
	}

	public static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}
}