def mismatch(a, b):
    return sum(x != y for x, y in zip(a, b))



def calculate_offtargets(genome, guide):

    hits = 0

    for i in range(len(genome) - len(guide)):

        target = genome[i:i+len(guide)]

        mm = mismatch(guide, target)

        if mm <= 2:
            hits += 1

    return hits * 0.1