#!/usr/bin/python
from __future__ import division
import random

def spin_is_red():
    return random.randrange(38) < 18

def play(turns, start=0, responsibly=False):
    bank = start
    bet = 1
    
    for i in xrange(turns):
        if responsibly and bet > bank:
            break
        if spin_is_red():
            bank += bet
            bet = 1
        else:
            bank -= bet
            bet *= 2
    return bank - start

def main():
    start = 100
    trials = 1000
    turns = 1000
    total = 0
    
    for i in xrange(trials):
        total += play(turns, responsibly = False) # the way to millions...slowly
        # total += play(turns, start = start, responsibly = True) # lose
    
    print("Expected payout: %s\n" % (total / trials))

main()