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import random

import math

def f(x, y):

    return math.sqrt(x**2 - y**2)

n = 100000

sum_f = 0

for _ in range(n):

    x = random.random()

    y = random.random() * x

    sum_f += f(x, y)

S = 0.5

I = S * (sum_f / n)

print(I)