import sys
import string


def distance_from_edge(N, x, y):
    """Return the distance of (x,y) from the edge of an NxN square.

    The returned value will be in [0,N-1].
    """

    size = 2*N - 1      # could pass as param, but...

    # force x and y coords to be in top-left quadrant
    if x >= N:
        x = size - 1 - x
    if y >= N:
        y = size - 1 - y

    # figure out the distance from edge in TL quadrant
    if y <= x:
        return y
    return x


# get the desired size from the command line
if len(sys.argv) != 2:
    print('Usage: test.py N')
    sys.exit(1)

try:
    N = int(sys.argv[1])
except ValueError:
    print('The N value must be an integer value, 1 to 26 inclusive.')
    sys.exit(1)

if not (1 <= N <= 26):
    print('The N value must be an integer value, 1 to 26 inclusive.')
    sys.exit(1)

# calculate "size" and the characters we will need
size = 2*N - 1
chars = string.ascii_uppercase[:N]

# print the square, substituting the character for the distance integer
for y in range(size):
    for x in range(size):
        ch = chars[distance_from_edge(N, x, y)]
        print(ch, end='')
    print()     # finish the row