Finding longest substring in alphabetical order

Question

EDIT: I am aware that a question with similar task was already asked in SO but I\'m interested to find out the problem in this specific piece of code. I am

Answer 1

first_seq=s[0]
break_seq=s[0]
current = s[0]
for i in range(0,len(s)-1):
    if s[i]<=s[i+1]:
        first_seq = first_seq + s[i+1]
        if len(first_seq) > len(current):
            current = first_seq
    else:
        first_seq = s[i+1]
        break_seq = first_seq
print("Longest substring in alphabetical order is: ", current)