Problem:
Score: 300 points

Problem Statement

Consider an analog clock whose hour and minute hands are A and B centimeters long, respectively.

An endpoint of the hour hand and an endpoint of the minute hand are fixed at the same point, around which each hand rotates clockwise at constant angular velocity. It takes the hour and minute hands 12 hours and 1 hour to make one full rotation, respectively.

At 0 o'clock, the two hands overlap each other. H hours and M minutes later, what is the distance in centimeters between the unfixed endpoints of the hands?

Constraints

All values in input are integers.

1 \leq A, B \leq 1000

0 \leq H \leq 11

0 \leq M \leq 59

Input

Input is given from Standard Input in the following format:

A B H M

Output

Print the answer without units. Your output will be accepted when its absolute or relative error from the correct value is at most 10^{-9}.

Sample Input 1

3 4 9 0

Sample Output 1

5.00000000000000000000

The two hands will be in the positions shown in the figure below, so the answer is 5 centimeters.

Sample Input 2

3 4 10 40

Sample Output 2

4.56425719433005567605

The two hands will be in the positions shown in the figure below. Note that each hand always rotates at constant angular velocity.

Solution in Go (1.14.1) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"reflect"
	"strconv"
)

const INFINITY = math.MaxInt64/2 - 1

func exec(stdin *Stdin, stdout *Stdout) {
	a := stdin.ReadFloat64() // 短針
	b := stdin.ReadFloat64() // 長針
	h := stdin.ReadFloat64()
	m := stdin.ReadFloat64()

	x := 360.0 / 720.0 * (h*60.0 + m)
	y := 360.0 / 60.0 * m
	z := math.Abs(x - y)
	if 360.0-z < z {
		z = 360.0 - z
	}

	stdout.Println(math.Sqrt(a*a + b*b - 2.0*a*b*math.Cos(z*math.Pi/180.0)))
}

func main() {
	stdout := NewStdout()
	defer stdout.Flush()
	exec(NewStdin(bufio.ScanWords), stdout)
}

type Stdin struct {
	stdin *bufio.Scanner
}

func NewStdin(split bufio.SplitFunc) *Stdin {
	s := Stdin{bufio.NewScanner(os.Stdin)}
	s.stdin.Split(split)
	s.stdin.Buffer(make([]byte, bufio.MaxScanTokenSize), INFINITY)
	return &s
}

func (s *Stdin) Read() string {
	s.stdin.Scan()
	return s.stdin.Text()
}

func (s *Stdin) ReadInt() int {
	n, _ := strconv.Atoi(s.Read())
	return n
}

func (s *Stdin) ReadFloat64() float64 {
	n, _ := strconv.ParseFloat(s.Read(), 64)
	return n
}

func (s *Stdin) ReadIntSlice(n int) []int {
	a := make([]int, n)
	for i := 0; i < n; i++ {
		a[i] = s.ReadInt()
	}
	return a
}

func (s *Stdin) ReadStringSlice(n int) []string {
	a := make([]string, n)
	for i := 0; i < n; i++ {
		a[i] = s.Read()
	}
	return a
}

func (s *Stdin) ReadFloat64Slice(n int) []float64 {
	a := make([]float64, n)
	for i := 0; i < n; i++ {
		a[i] = s.ReadFloat64()
	}
	return a
}

type Stdout struct {
	stdout *bufio.Writer
}

func NewStdout() *Stdout {
	return &Stdout{bufio.NewWriter(os.Stdout)}
}

func (s *Stdout) Flush() {
	s.stdout.Flush()
}

func (s *Stdout) Println(a ...interface{}) {
	fmt.Fprintln(s.stdout, a...)
}

func Min(a int, b ...int) int {
	for _, v := range b {
		if v < a {
			a = v
		}
	}
	return a
}

func Max(a int, b ...int) int {
	for _, v := range b {
		if a < v {
			a = v
		}
	}
	return a
}

func Abs(x int) int {
	if x > 0 {
		return x
	} else {
		return x * -1
	}
}

func Pow(x, y int) int {
	z := 1
	for y > 0 {
		if y%2 == 0 {
			x *= x
			y /= 2
		} else {
			z *= x
			y -= 1
		}
	}
	return z
}

func IsPrime(x int) bool {
	if x < 2 {
		return false
	}

	for i := 2; i*i <= x; i++ {
		if x%i == 0 {
			return false
		}
	}
	return true
}

func Gcd(x, y int) int {
	if x < y {
		x, y = y, x
	}

	for y > 0 {
		x, y = y, x%y
	}

	return x
}

func Lcm(x, y int) int {
	return x * y / Gcd(x, y)
}

func CeilDiv(x, y int) int {
	if x%y == 0 {
		return x / y
	} else {
		return x/y + 1
	}
}

func LCS(s, t string) string {
	n := len(s)
	m := len(t)
	dp := make([][]int, n+1)
	for i := 0; i <= n; i++ {
		dp[i] = make([]int, m+1)
	}

	for i := 1; i <= n; i++ {
		for j := 1; j <= m; j++ {
			if s[i-1] == t[j-1] {
				dp[i][j] = dp[i-1][j-1] + 1
			} else {
				dp[i][j] = Max(dp[i-1][j], dp[i][j-1])
			}
		}
	}

	x := n
	y := m
	u := make([]byte, dp[n][m])
	i := dp[n][m] - 1
	for x > 0 && y > 0 {
		if dp[x][y] == dp[x-1][y] {
			x--
		} else if dp[x][y] == dp[x][y-1] {
			y--
		} else {
			x--
			y--
			u[i] = s[x]
			i--
		}
	}

	return string(u)
}

// [0..n) から r個選んだ組合せを生成する。
// r < 0 の場合はすべての組合せを生成する。
func Combinations(n int, r int) [][]int {
	a := [][]int{}
	for i := uint(0); i < (1 << uint(n)); i++ {
		b := []int{}
		for j := uint(0); j < uint(n); j++ {
			if i&(uint(1)<<j) != 0 {
				b = append(b, int(j))
			}
		}

		if r < 0 || len(b) == r {
			a = append(a, b)
		}
	}
	return a
}

// [0..n)の順列を生成する。
func Permutations(n int) [][]int {
	type e struct {
		bit uint
		a   []int
	}

	q := []*e{}
	for i := 0; i < n; i++ {
		q = append(q, &e{bit: 1 << uint(i), a: []int{i}})
	}

	p := [][]int{}
	for x := 0; x < len(q); x++ {
		cur := q[x]
		if cur.bit == (1<<uint(n) - 1) {
			p = append(p, cur.a)
			continue
		}

		for i := 0; i < n; i++ {
			if cur.bit&(1<<uint(i)) != 0 {
				continue
			}

			m := len(cur.a) + 1
			b := make([]int, m)
			copy(b, cur.a)
			b[m-1] = i
			q = append(q, &e{bit: cur.bit | (1 << uint(i)), a: b})
		}
	}
	return p
}

func ReverseSlice(v interface{}) {
	if reflect.TypeOf(v).Kind() == reflect.Slice {
		slice := reflect.ValueOf(v)
		for i1, n := 0, slice.Len(); i1 < n/2; i1++ {
			i2 := n - i1 - 1
			v1 := reflect.ValueOf(slice.Index(i1).Interface())
			slice.Index(i1).Set(slice.Index(i2))
			slice.Index(i2).Set(v1)
		}
	}
}

func ReverseString(s string) string {
	t := []rune(s)
	ReverseSlice(t)
	return string(t)
}

func ToStringSlice(slice interface{}) []string {
	// 本来はerrを返却すべき。 利用する側(=自分)は引数がsliceであることを知っている。
	if reflect.TypeOf(slice).Kind() != reflect.Slice {
		panic(fmt.Sprintf("%v is not slice", slice))
	}

	src := reflect.ValueOf(slice)
	n := src.Len()
	dst := make([]string, n)
	for i := 0; i < n; i++ {
		dst[i] = fmt.Sprintf("%v", src.Index(i))
	}
	return dst
}