#!/usr/bin/env python

try:

input = raw_input

except:

pass

def dispense(x):

if x <= 0 or x % 10 or x in (10, 30):

raise KeyError

q = x // 50

if (x - 50 * q) % 20:

q -= 1

return tuple([q, (x - q * 50) // 20])

while True:

try:

amt = dispense(int(input('Enter amount to turn into $20 and $50 notes: ')))

msg = ''

if amt[0]:

msg += '%s x $50' % amt[0]

if amt[0] and amt[1]:

msg += ', '

if amt[1]:

msg += '%s x $20' % amt[1]

print(msg)

except (KeyError, ValueError):

print('Invalid amount. Must be able to make up the total using $20 and $50 notes.')

except (KeyboardInterrupt, EOFError):

break