''' 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 + 1 ) :
    # print a line of the form i: 0 1 2 ... i
    print( i, ':', end=' ' )
    for lv in range(0, i + 1):  # 0 to i
        # print a line of the form i: 0 1 2 ... i (range(0, i+1))
        print(lv, end=' ')  # How can I change this???
    print() # prints a blank line/tells you to go to the next line

# It's important to keep in mind the indentation of your
# statements in your for loop.
# What are we doing for each loop variable value? The statements indented
# into it!

# It's important to visualize how a nested loop works. We should keep
# the values of i and lv in mind as we run through this loop
# and we should know that for each value of i, we are doing
# three things (print i:, print all values leading up to i, and
# print out a blank line after that to separate each line of output)

    # 0: comes from line 16
    # 0: 0
    #    ^ this part right here comes from lines 17-19
    # 1: comes from line 16
    # 1: 01
    #    ^ this part comes from lines 17-19