''' Purpose: introduce nested looping.
        for a user-supplied n, loop n times, where on the ith iteration
        the integers from 0 to i are printed out.
'''

import time

# get n
reply = input( 'Enter number: ' )
n = int( reply )

# performed the repeated printing of a number series
for i in range( 0, n ) :
    # print a line of the form i: 0 1 2 ... i