I try to make a simple game, give a sum random number and input to answer it, I try to limit the time for input, but I can stop the input processing when timeout.

```
score=0
from threading import Timer
while score<=3:
    import random
    a=random.randint(0,100)
    b=random.randint(0,100)
    sum=a+b
    d=str(sum)
    while True:
        print(a,"+",b,"=")
        timeout = 3
        t = Timer(timeout, print, ['Sorry, times up'])
        t.start()
        prompt = "you have %d s to input your answer\n" % timeout
        c = input(prompt)
        t.cancel()

          #i want to stop input c and make other code like 'do you want to play again'
        if c.isdigit():
            break
        else:
            print('invalid input')
        continue
    result=c
    if result==d:
        score=score+1
        print('your score',score)
    else:
        score=score-1
        print('your score',score)
else:
    print('you win')

```