def hamming_distance(txt1, txt2):
 count=0
 for i in range(len(txt1)):
        if(txt1[i] != txt2[i]):
            count=count+1
 return count
print(hamming_distance("abcde", "bcdef"))
print(hamming_distance("abcde", "abcde"))
print(hamming_distance("strong", "strung"))                 
     