def fitness(position):
key = "".join(alphabet[i] for i in position)
substitution = Substitution(alphabet, key)
original_text = substitution.decrypt(cyphertext)
frequency = Frequency(n_gram, alphabet)
frequency.get_frequency(original_text)
res = 0
for i in range(len(n_gram)):
for j in range(len(frequency.ftab[i])):
res += alpha[i] * abs(frequency.ftab[i][j] - target.ftab[i][j])
return res
