import sys
# from random import choice,randint
# from bisect import bisect_left as bl             
# from bisect import bisect_right as br  
# from collections import deque,defaultdict,Counter
# from math import sqrt,floor,ceil
# from itertools import combinations,permutations
# from heapq import heapify,heappop,heappush,heappushpop
# inp=sys.stdin.readline
# out=sys.stdout.write
# flsh=sys.stdout.flush
# ranomd string generator --> a = ''.join(random.choices(string.ascii_lowercase, k = 1000))
 
sys.setrecursionlimit(10**9)
inf = 10**20
eps = 1.0 / 10**10
mod = 10**9+7
mod1=998244353
dd = [(-1,0),(0,1),(1,0),(0,-1)]
ddn = [(-1,0),(-1,1),(0,1),(1,1),(1,0),(1,-1),(0,-1),(-1,-1)]

#fact=[1]
#for i in range(1,100001):
#    fact.append((fact[-1]*i)%mod)
#ifact=[0]*100001
#ifact[100000]=pow(fact[100000],mod-2,mod)
#for i in range(100000,0,-1):
#    ifact[i-1]=(i*ifact[i])%mod
 
def MI(): return map(int, inp().strip().split())
def LI(): return list(map(int, inp().strip().split()))
def LLI(): return [list(map(int, l.split())) for l in sys.stdin.readlines().strip()]
def LI_(): return [int(x)-1 for x in inp().strip().split()] #use list comprehension for loops
def LF(): return [float(x) for x in inp().strip().split()] #use try and except for dictionaries
def LS(): return inp().strip().split() #declare local variables ... for functions assing them to variables
def I(): return int(inp().strip()) # before using example ... func = len for using len() funtcion
def F(): return float(inp().strip()) #sort dictionary after zipping
def S(): return inp().strip() #use map function for mapping list to a fuction
def pf(s): return out(s+'\n')
def JA(a, sep): return sep.join(map(str, a)) #use this for string concatenation
def JAA(a, s, t): return s.join(t.join(map(str, b)) for b in a)
def modinv(n,p):return pow(n,p-2,p)
def ncr(n,r,p):                      
    t=((fact[n])*((ifact[r]*ifact[n-r])%p))%p
    return t

####################Actualcode################################

# Python program to find angle 
# between hour and minute hands 

# Function to Calculate angle b/w 
# hour hand and minute hand 
def calcAngle(h,m): 
		if (h == 12): 
			h = 0
		if (m == 60): 
			m = 0
		hour_angle = 0.5 * (h * 60 + m) 
		minute_angle = 6 * m 
		angle = abs(hour_angle - minute_angle) 
		angle = min(360 - angle, angle) 
		return angle 

def main():
    from math import cos,sqrt,radians
    a,b,h,m=MI()
    x = calcAngle(h,m)
    # print(x)
    x = radians(x)
    c = sqrt((a*a)+(b*b)-(2*a*b)*(cos(x)))
    print(c)




######## Python 2 and 3 footer by Pajenegod and c1729
py2 = round(0.5)
if py2:
    from future_builtins import ascii, filter, hex, map, oct, zip
    range = xrange

import os, sys
from io import IOBase, BytesIO

BUFSIZE = 8192
class FastIO(BytesIO):
    newlines = 0
    def __init__(self, file):
        self._file = file
        self._fd = file.fileno()
        self.writable = "x" in file.mode or "w" in file.mode
        self.write = super(FastIO, self).write if self.writable else None

    def _fill(self):
        s = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
        self.seek((self.tell(), self.seek(0,2), super(FastIO, self).write(s))[0])
        return s
    def read(self):
        while self._fill(): pass
        return super(FastIO,self).read()

    def readline(self):
        while self.newlines == 0:
            s = self._fill(); self.newlines = s.count(b"\n") + (not s)
        self.newlines -= 1
        return super(FastIO, self).readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.getvalue())
            self.truncate(0), self.seek(0)

class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        if py2:
            self.write = self.buffer.write
            self.read = self.buffer.read
            self.readline = self.buffer.readline
        else:
            self.write = lambda s:self.buffer.write(s.encode('ascii'))
            self.read = lambda:self.buffer.read().decode('ascii')
            self.readline = lambda:self.buffer.readline().decode('ascii')

sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)

inp = lambda: sys.stdin.readline().rstrip('\r\n')
out = lambda x: sys.stdout.write(x)
flsh= lambda: sys.stdout.flush()

if __name__ == "__main__":
    main()

### FIXED CODE ###

import sys
# from random import choice,randint
# from bisect import bisect_left as bl             
# from bisect import bisect_right as br  
# from collections import deque,defaultdict,Counter
# from math import sqrt,floor,ceil
# from itertools import combinations,permutations
# from heapq import heapify,heappop,heappush,heappushpop
# inp=sys.stdin.readline
# out=sys.stdout.write
# flsh=sys.stdout.flush
# ranomd string generator --> a = ''.join(random.choices(string.ascii_lowercase, k = 1000))
 
sys.setrecursionlimit(10**9)
inf = 10**20
eps = 1.0 / 10**10
mod = 10**9+7
mod1=998244353
dd = [(-1,0),(0,1),(1,0),(0,-1)]
ddn = [(-1,0),(-1,1),(0,1),(1,1),(1,0),(1,-1),(0,-1),(-1,-1)]

#fact=[1]
#for i in range(1,100001):
#    fact.append((fact[-1]*i)%mod)
#ifact=[0]*100001
#ifact[100000]=pow(fact[100000],mod-2,mod)
#for i in range(100000,0,-1):
#    ifact[i-1]=(i*ifact[i])%mod
 
def MI(): return map(int, inp().strip().split())
def LI(): return list(map(int, inp().strip().split()))
def LLI(): return [list(map(int, l.split())) for l in sys.stdin.readlines().strip()]
def LI_(): return [int(x)-1 for x in inp().strip().split()] #use list comprehension for loops
def LF(): return [float(x) for x in inp().strip().split()] #use try and except for dictionaries
def LS(): return inp().strip().split() #declare local variables ... for functions assing them to variables
def I(): return int(inp().strip()) # before using example ... func = len for using len() funtcion
def F(): return float(inp().strip()) #sort dictionary after zipping
def S(): return inp().strip() #use map function for mapping list to a fuction
def pf(s): return out(s+'\n')
def JA(a, sep): return sep.join(map(str, a)) #use this for string concatenation
def JAA(a, s, t): return s.join(t.join(map(str, b)) for b in a)
def modinv(n,p):return pow(n,p-2,p)
def ncr(n,r,p):                      
    t=((fact[n])*((ifact[r]*ifact[n-r])%p))%p
    return t

####################Actualcode################################
def main():
    n = I()
    if n%10 in [2,4,5,7,9]:
        print("hon")
    elif n%10 in [0,1,6,8]:
        print("pon")
    elif n%10==3:
        print("bon")


######## Python 2 and 3 footer by Pajenegod and c1729
py2 = round(0.5)
if py2:
    from future_builtins import ascii, filter, hex, map, oct, zip
    range = xrange

import os, sys
from io import IOBase, BytesIO

BUFSIZE = 8192
class FastIO(BytesIO):
    newlines = 0
    def __init__(self, file):
        self._file = file
        self._fd = file.fileno()
        self.writable = "x" in file.mode or "w" in file.mode
        self.write = super(FastIO, self).write if self.writable else None

    def _fill(self):
        s = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
        self.seek((self.tell(), self.seek(0,2), super(FastIO, self).write(s))[0])
        return s
    def read(self):
        while self._fill(): pass
        return super(FastIO,self).read()

    def readline(self):
        while self.newlines == 0:
            s = self._fill(); self.newlines = s.count(b"\n") + (not s)
        self.newlines -= 1
        return super(FastIO, self).readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.getvalue())
            self.truncate(0), self.seek(0)

class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        if py2:
            self.write = self.buffer.write
            self.read = self.buffer.read
            self.readline = self.buffer.readline
        else:
            self.write = lambda s:self.buffer.write(s.encode('ascii'))
            self.read = lambda:self.buffer.read().decode('ascii')
            self.readline = lambda:self.buffer.readline().decode('ascii')

sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)

inp = lambda: sys.stdin.readline().rstrip('\r\n')
out = lambda x: sys.stdout.write(x)
flsh= lambda: sys.stdout.flush()

if __name__ == "__main__":
    main()