Keep score for Rosenthal's centipede game

centipede.py

"""
A script to keep score for a version of Rosenthal's centipede game.
The rules are:
1. There are two players.
2. At the beginning of the game the players have 1 point each.
3. The players get turns alternately.
4. On their turn a player can choose to continue (C) or stop (S).
5. If the player chooses C, 1 point is taken from their account
   and 2 points are added to the other player's account.
6. If the player chooses S, the game stops.
7. If after any step both players have exactly MAX points, the game stops.

Usage: python centipede.py [MAX]

The default value of max is 100
"""

from sys import argv

max=100
if len(argv)>1:
    n=int(argv[1])
    if n>1:
        max=n

k=[1,1]
i=0

while k[0]!=max or k[1]!=max:
    p="[%d,%d]\tPlayer %d: C/s? "%(k[0],k[1],i+1)
    ans="X"
    while ans!="S" and ans!="C" and ans!="s" and ans!="c" and ans!="":
        ans=raw_input(p)
    if ans=="S" or ans=="s":
        break
    k[i]=k[i]-1
    k[1-i]=k[1-i]+2
    i=1-i
print "[%d,%d]"%(k[0],k[1])