#!/usr/bin/env python

from operator import add, sub

from random import randint, choice

ops = {'+': add, '-': sub}

MAXTRIES = 2

def doprob():

op = choice('+-')

nums = [ randint(1,10) for i in range(2) ]

nums.sort(reverse=True)

ans = ops[op](*nums)

pr = '%d %s %s = ' % (nums[0], op, nums[1])

oops = 0

while True:

try:

if int(raw_input(pr)) == ans:

print 'correct'

break

if oops == MAXTRIES:

print 'sorry... the answer is\n%s%d' % (pr, ans)

else:

print 'incorrect... try again'

oops += 1

except (KeyboardInterrupt,

EOFError, ValueError):

print 'invalid input... try again'

def main():

while True:

doprob()

try:

opt = raw_input('Again? [y] ').lower()

if opt and opt[0] == 'n':

break

except (KeyboardInterrupt, EOFError):

break

if __name__ == '__main__':

main()