hello...can someone please tell me how to fix the bug in this code, I tried all i could but...am here..

ordered substring

kip = []
s = raw_input('give me a string: ')
v = s[len(s) - 1]
for a in range(len(s)):
    store = s[a]
    for i in range(len(s)):
        z = v == s[len(s) - 1]
        if z == True:
            c = (i + 1 >= len(s)) 
            if c == False:
                while s[i] < s[i + 1]:
                    if store == '':
                        store = s[i]
                    store += s[i + 1]
                    s = s.translate(None, s[i])
                kip.append(store)
                store = ''
        else:
            break
        kip.append(store)
        store = ''
Lngst = len(max(kip,key=len))      # key=len takes length in consideration 
for i in range(0,len(kip)):
    d = len(kip[i])
    if d == Lngst:   
        print 'Longest substring in alphabetical order is:' + str(kip[i])
        break