import random

G="gold"
S="silver"
boxes=[[G,G],[G,S],[S,S]];

count = 0;
count2 = 0;
for i in xrange(100000):
        box = random.choice(boxes)
        i = random.randrange(2)
        ball1 = box[i]
        ball2 = box[i-1]
        if (ball1 == G):
                count += 1
                if (ball2 == G):
                        count2 += 1

print (1.0*count2)/(1.0*count)