using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using System.Globalization;
using System.Diagnostics;
 
class Solve
{
    
    public Solve() { }
    public static int Main()
    {
        new Solve().calc();
        return 0;
    }
 
 
    Scanner cin;
 
    void calc()
    {
        cin = new Scanner();
        var A = cin.nextInt(); // 時針
        var B = cin.nextInt(); // 分針
        var H = cin.nextInt(); // 時
        var M = cin.nextInt(); // 分
 
        var radA = 30.0 * H / 360.0 + 6.0 * M / 360.0 / 12.0;
        var radB = 6.0 * M / 360.0;
        var theta = Math.Abs(2.0 * Math.PI * (radA - radB));
 
        // 余弦定理
        // a^2 = b^2 + c^2 - 2 * b * c * cos(theta);
        var square = A * A + B * B - 2.0 * A * B * Math.Cos(theta);
        var result = Math.Sqrt(square);
 
        Console.WriteLine(result);
    }
}
class Modulo
{
    private const int M = 1000000007;
    private readonly int[] m_facs;
    public int Mul(int a, int b)
    {
        return (int)(Math.BigMul(a, b) % M);
    }
    public Modulo(int n)
    {
        m_facs = new int[n + 1];
        m_facs[0] = 1;
        for (int i = 1; i <= n; ++i)
        {
            m_facs[i] = Mul(m_facs[i - 1], i);
        }
    }
    public int Fac(int n)
    {
        return m_facs[n];
    }
    public int Pow(int a, int m)
    {
        switch (m)
        {
        case 0:
            return 1;
        case 1:
            return a;
        default:
            int p1 = Pow(a, m / 2);
            int p2 = Mul(p1, p1);
            return ((m % 2) == 0) ? p2 : Mul(p2, a);
        }
    }
    public int Div(int a, int b)
    {
        return Mul(a, Pow(b, M - 2));
    }
    public int Ncr(int n, int r)
    {
        if (n < r) { return 0; }
        if (n == r) { return 1; }
        int res = Fac(n);
        res = Div(res, Fac(r));
        res = Div(res, Fac(n - r));
        return res;
    }
}
 
class Scanner
{
    string[] s;
    int i;
 
    char[] cs = new char[] { ' ' };
 
    public Scanner()
    {
        s = new string[0];
        i = 0;
    }
 
    public string next()
    {
        if (i < s.Length) return s[i++];
        string st = Console.ReadLine();
        while (st == "") st = Console.ReadLine();
        s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
        if (s.Length == 0) return next();
        i = 0;
        return s[i++];
    }
 
    public int nextInt()
    {
        return int.Parse(next());
    }
    public int[] ArrayInt(int N, int add = 0)
    {
        int[] Array = new int[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextInt() + add;
        }
        return Array;
    }
 
    public long nextLong()
    {
        return long.Parse(next());
    }
 
    public long[] ArrayLong(int N, long add = 0)
    {
        long[] Array = new long[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextLong() + add;
        }
        return Array;
    }
 
    public double nextDouble()
    {
        return double.Parse(next());
    }
 
 
    public double[] ArrayDouble(int N, double add = 0)
    {
        double[] Array = new double[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextDouble() + add;
        }
        return Array;
    }
}

Measured memory_bytes: 27896