#! /usr/bin/env python
# ulam or 3n+1 conjecture: 
# python illustration by o. knill, 8/6/2001

def ulam(n):
   k=0
   while n>1:
     k=k+1
     if n % 2==0: 
       n=n/2 
     else: 
       n=3*n+1
   return k

def main():
   i=2 
   max=1
   limit=10000000000L
   show_frequency=1000
   while i <= limit:
     i=i+1
     l=ulam(i)
     if l>max:
        max=l; 
     if i % show_frequency==0:
        print "Maximal number of iterations needed until",i,":  ",max

main()