from __future__ import print_function largest_number = 0 pre_counter = 0 for input1 in range(750000,1000000): counter = 1 number = input1 while number > 1: if number % 2 == 0: number /=2 counter += 1 else: number = (3*number)+1 counter += 1 if counter > pre_counter: largest_number = input1 pre_counter = counter print(('Largest Number:',largest_number,'->',pre_counter,'digits'))