SPOJ - http://www.spoj.com/problems/PROBTNPO/

PROBTNPO.py

import sys
cache = {}
while True:
    c = sys.stdin.readline()
    if c == '': break
    a1, b1 = c.split()    
    a = int(a1); b = int(b1)
    max_length = 0   
    a, b = min(a,b), max(a,b)
    if a < b/2: a = b/2   
    for i in range(a, b+1):
        i1 = i
        cached = False        
        length = 0
        while i != 1:
            if i in cache:        
                length += cache[i]    
                cached = True         
                break
            if i%2 == 0:          
                i = i >> 1            
                length += 1           
            else:    
                i = i + (i >> 1) + 1  
                length += 2           
        if not cached: length += 1
        if i1 not in cache: cache[i1] = length
        if length > max_length: max_length = length
    print(a1+" "+b1+" "+str(max_length))