#!/usr/bin/python3

from itertools import count
import random

from util.io import readvalue

def peter_coin_series(randf = random.randint):
	result = 0

	for k in count(1):
		if(randf(0, 1) < 0.5):
			return (result, k)
		result += 2**k



if( __name__ == "__main__"):
	
	def positive_int(s):
		i = int(s)
		if(i <= 0):
			raise ValueError("{} is negative".format(i))
		return i

	print("I am going to toss a coin many times.\n" 
		"You are going to win 2**k if no head appears afer k throws.\n")

	bet = readvalue("How many ducats do you want to bet? ", positive_int)
	result, throws = peter_coin_series()

	win = bet - result

	if(win < 0):
		print("Bad, A head came out on throw #{}. You lost {} ducats.".format(throws, -win))
	else:
		print("You won {} ducats.".format(win))