using System;
using System.Collections.Generic;
using System.Linq;
using static System.Math;

namespace CSharp
{
    static class Program
    {
        static (double X, double Y) GetPoint(int length, double degree)
        {
            return (length * Cos(PI / 2 - degree), length * Sin(PI / 2 - degree));
        }

        static double Distance((double X, double Y) a, (double X, double Y) b)
        {
            static double Square(double value) => value * value;
            return Sqrt(Square(a.X - b.X) + Square(a.Y - b.Y));
        }

        static void Main(string[] args)
        {
            ReadInt(out var a, out var b, out var h, out var m);
            var hour = GetPoint(a, 2 * PI / 12 * h + 2 * PI / 12 * (m / 60.0));
            var minute = GetPoint(b, 2 * PI * (m / 60.0));
            double distance = Distance(hour, minute);
            Console.WriteLine($"{distance:0.000000000000000000}");
        }

        #region Helpers

        static int[] ReadIntArray() => Console.ReadLine().Split().Select(s => int.Parse(s)).ToArray();
        static long[] ReadLongArray() => Console.ReadLine().Split().Select(s => long.Parse(s)).ToArray();

        static int[] ReadLineIntArray(int count) => Enumerable.Repeat(0, count).Select(_ => int.Parse(Console.ReadLine())).ToArray();
        static long[] ReadLineLongArray(int count) => Enumerable.Repeat(0, count).Select(_ => long.Parse(Console.ReadLine())).ToArray();

        static string ReadString() => Console.ReadLine();
        static int ReadInt() => int.Parse(Console.ReadLine());
        static long ReadLong() => long.Parse(Console.ReadLine());

        static void ReadInt(out int first)
        {
            var array = ReadIntArray();
            first = array[0];
        }

        static void ReadInt(out int first, out int second)
        {
            var array = ReadIntArray();
            first = array[0];
            second = array[1];
        }

        static void ReadInt(out int first, out int second, out int third)
        {
            var array = ReadIntArray();
            first = array[0];
            second = array[1];
            third = array[2];
        }

        static void ReadInt(out int first, out int second, out int third, out int fourth)
        {
            var array = ReadIntArray();
            first = array[0];
            second = array[1];
            third = array[2];
            fourth = array[3];
        }

        static void ReadLong(out long first)
        {
            var array = ReadLongArray();
            first = array[0];
        }

        static void ReadLong(out long first, out long second)
        {
            var array = ReadLongArray();
            first = array[0];
            second = array[1];
        }

        static void ReadLong(out long first, out long second, out long third)
        {
            var array = ReadLongArray();
            first = array[0];
            second = array[1];
            third = array[2];
        }

        static void ReadLong(out long first, out long second, out long third, out long fourth)
        {
            var array = ReadLongArray();
            first = array[0];
            second = array[1];
            third = array[2];
            fourth = array[3];
        }

        static string YesNo(bool condition) => condition ? "Yes" : "No";
        static string YESNO(bool condition) => condition ? "YES" : "NO";

        #endregion
    }
}

Measured memory_bytes: 28700