#!/bin/python3

# Simulacion numerica del problema 1c de la guia 2. (FT3 2Cuat 2018)
from random import seed
from random import randint

# seed random number generator
seed()

n_exp = 180000 # number of experiments
n_fav = 0 # number of favorable cases

for i_exp in range(n_exp):
    urna_A=["b","b","b","b","b","b","b","n","n","n"]
    urna_B=["b","b","b","b","b","n","n","n","n","n"]
    
    # Select ball from A
    nro_bola_A = randint(0, len(urna_A) - 1) # raffle which ball do I take from A
    bola_extraida_A = urna_A[nro_bola_A] # Select that ball from A
    
    #Meto bola extraida en urna A en urna B
    urna_B.append( bola_extraida_A )
    
    #Select ball from B
    nro_bola_B = randint(0, len(urna_B) - 1) # raffle which ball do I take from B
    bola_extraida_B = urna_B[nro_bola_B]
    
    if bola_extraida_B == "n" and bola_extraida_A == "n": 
        n_fav += 1

print( float(n_fav) / float(n_exp) )