# Assume s is a string of lower case characters.

# Write a program that prints the longest substring of s in which
# the letters occur in alphabetical order. For example,
# if s = 'azcbobobegghakl', then your program should print

# Longest substring in alphabetical order is: beggh

# In the case of ties, print the first substring. For example,
# if s = 'abcbcd', then your program should print

# Longest substring in alphabetical order is: abc
