1
def isqrt(n):
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    return int(floor(sqrt(n)))
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4
def usqrt (n):
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    ur = isqrt(n)
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    if ur ** 2 < n:
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        ur = ur + 1
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    return(ur)
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def FermatAttack (n, rounds):
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    st = usqrt(n)
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    for x in range(st, st + rounds + 1):
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        sq = x ** 2 - n
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        y = isqrt(sq)
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        if y ** 2 == sq:
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            print("Factor found in round {0}".format( x - st + 1))
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            return(x + y)
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    print("No factors found in {0}".format( rounds))
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