@file:Suppress("NOTHING_TO_INLINE", "EXPERIMENTAL_FEATURE_WARNING", "OVERRIDE_BY_INLINE")

import java.io.PrintWriter
import kotlin.math.*
import kotlin.random.Random
import kotlin.collections.sort as _sort
import kotlin.collections.sortDescending as _sortDescending
import kotlin.io.println as iprintln

/** @author Spheniscine */
fun main() { _writer.solve(); _writer.flush() }
fun PrintWriter.solve() {
//    val numCases = readInt()
//    for(case in 1..numCases) {
//        //print("Case #$case: ")
//
//    }

    val a = readDouble()
    val b = readDouble()
    val h = readInt()
    val m = readInt()

    val hm = h * 60 + m

    val ha = TAU * hm / (12*60)
    val hx = cos(ha) * a
    val hy = sin(ha) * a

    val ma = TAU * m / 60
    val mx = cos(ma) * b
    val my = sin(ma) * b

    val ans = hypot(hx - mx, hy - my)

    println(ans)
}

const val TAU = PI * 2

infix fun Int.divCeil(other: Int) =
    (this / other).let { if(xor(other) >= 0 && it * other != this) it+1 else it }

inline infix fun Int.divFloor(other: Int) = Math.floorDiv(this, other)

infix fun Long.divCeil(other: Long) =
    (this / other).let { if(xor(other) >= 0 && it * other != this) it+1 else it }

inline infix fun Long.divFloor(other: Long) = Math.floorDiv(this, other)

/** IO */
//@JvmField val INPUT = File("input.txt").inputStream()
//@JvmField val OUTPUT = File("output.txt").outputStream()
@JvmField val INPUT = System.`in`
@JvmField val OUTPUT = System.out

@JvmField val _reader = INPUT.bufferedReader()
fun readLine(): String? = _reader.readLine()
fun readLn() = _reader.readLine()!!
@JvmField var _ln = ""
@JvmField var _lnPtr = 0
fun read(): String {
    while (_lnPtr >= _ln.length) {
        _ln = readLine() ?: return ""
        _lnPtr = 0
    }
    var j = _ln.indexOf(' ', _lnPtr)
    if(j < 0) j = _ln.length
    val res = _ln.substring(_lnPtr, j)
    _lnPtr = j + 1
    return res
}
fun readRem(): String /* reads remainder of current line */ =
    _ln.substring(min(_lnPtr, _ln.length)).also { _lnPtr = _ln.length }
fun readInt() = read().toInt()
fun readDouble() = read().toDouble()
fun readLong() = read().toLong()
fun readStrings(n: Int) = List(n) { read() }
fun readLines(n: Int) = List(n) { readLn() }
fun readInts(n: Int) = List(n) { read().toInt() }
fun readIntArray(n: Int) = IntArray(n) { read().toInt() }
fun readDoubles(n: Int) = List(n) { read().toDouble() }
fun readDoubleArray(n: Int) = DoubleArray(n) { read().toDouble() }
fun readLongs(n: Int) = List(n) { read().toLong() }
fun readLongArray(n: Int) = LongArray(n) { read().toLong() }

@JvmField val _writer = PrintWriter(OUTPUT, false)

/** shuffles and sort overrides to avoid quicksort attacks */
private inline fun <T> _shuffle(rnd: Random, get: (Int) -> T, set: (Int, T) -> Unit, size: Int) {
    // Fisher-Yates shuffle algorithm
    for (i in size - 1 downTo 1) {
        val j = rnd.nextInt(i + 1)
        val temp = get(i)
        set(i, get(j))
        set(j, temp)
    }
}

@JvmField var _random: Random? = null
val random get() = _random ?: Random(0x594E215C123 * System.nanoTime()).also { _random = it }

fun IntArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
fun IntArray.sort() { shuffle(); _sort() }
fun IntArray.sortDescending() { shuffle(); _sortDescending() }

fun LongArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
fun LongArray.sort() { shuffle(); _sort() }
fun LongArray.sortDescending() { shuffle(); _sortDescending() }

fun DoubleArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
fun DoubleArray.sort() { shuffle(); _sort() }
fun DoubleArray.sortDescending() { shuffle(); _sortDescending() }

fun CharArray.shuffle(rnd: Random = random) = _shuffle(rnd, ::get, ::set, size)
inline fun CharArray.sort() { _sort() }
inline fun CharArray.sortDescending() { _sortDescending() }

inline fun <T: Comparable<T>> Array<out T>.sort() = _sort()
inline fun <T: Comparable<T>> Array<out T>.sortDescending() = _sortDescending()
inline fun <T: Comparable<T>> MutableList<out T>.sort() = _sort()
inline fun <T: Comparable<T>> MutableList<out T>.sortDescending() = _sortDescending()

fun `please stop removing these imports IntelliJ`() { iprintln(max(1, 2)) }

/** additional commons */
inline fun <T> Iterable<T>.sumByLong(func: (T) -> Long) = fold(0L) { acc, t -> acc + func(t) }
inline fun <T> Sequence<T>.sumByLong(func: (T) -> Long) = fold(0L) { acc, t -> acc + func(t) }
inline fun <T> Array<T>.sumByLong(func: (T) -> Long) = fold(0L) { acc, t -> acc + func(t) }
fun IntArray.sumLong() = fold(0L, Long::plus)

Measured memory_bytes: 36124