Longest substring in Alphabetical order

#Python

'''
Find the longest substring in alphabetical order in the given string
'''

s = 'azcbobobegghakl'

i=1
subs=s[0]
subs2=s[0]
while(i<len(s)):
    j=i
    while(j<len(s)):
        if(s[j]>=s[j-1]):
            subs+=s[j]
            j+=1
        else:
            subs=subs.replace(subs[:len(subs)],s[i])  
            break
               
        if(len(subs)>len(subs2)):
            subs2=subs2.replace(subs2[:len(subs2)], subs[:len(subs)])
    subs=subs.replace(subs[:len(subs)],s[i])
       
    if(len(subs)==len(s)):
        subs2=subs2.replace(subs2[:len(subs2)], subs[:len(subs)])
        print "not here"   
        break;    
           
    i+=1
print "Longest substring in alphabetical order is:",subs2