''' Purpose: introduce nested looping.
        for a user-supplied n, loop n times, where on the rth iteration
        the integers from 0 to r-1 are printed out.
'''

import time

# Nested Loops
# for ... in ...:
    # for ... in ...:
        # statements

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

# performed the repeated printing of a number series
for r in range( 0, n ) : # r is each value from 0 to n - 1
    # print a line of the form row r : 0 1 2 ... r.  # to do so need to
    #   first print the row r: part.
    #   then on same line print out the values 0 1 2 ... r-1 one after the other
    print( 'row', r, ':' , end=' ' )
    for c in range(0, r + 1):  # c assumes each value from 0 to r + 1
        print(c, end=' ')  # print out each column value (c value) one by one on the same line separated by spaces
    print() # don't have the next output on the same line (print blank line on the new line)

# Again, you can name your loop variables whatever you want!
# r is not a specific indicator that we are going to be in a nested for loop.

# Normal (Single) Loop
# for ... in ...:
    # ...

# Nested Loop
# for ... in ...:
    # for ... in ...:
        # ...