#!/usr/bin/env python3
''' given a letter, print the text spiral of letters to that letter, e.g. G ->
G
F A B
E D C

There is a recursive solution of concentric rings:

21 22 23 24 25
20          10
19          11
18          12
17 16 15 14 13

    7  8  9
    6     2
    5  4  3

       1
'''
import math, sys

def layer(N, nrings):
    ''' return layer `N' of the spiral with `nrings' concentric rings '''
    outer = 2 * nrings - 1
    inner = outer - 2
    ring  = [1] if nrings == 1 else list(range(inner**2+1, outer**2+1))

    first = ring[-1*outer : ]
    left  = ring[-1*outer-N]
    right = ring[N-1]
    last  = ring[inner : inner+outer][::-1]

    if N == 0:
        return first
    elif 0 < N < outer - 1:
        return [left] + layer(N-1,nrings-1) + [right]
    else:
        return last

goal    = 'G' if len(sys.argv) == 1 else sys.argv[1]
nchars  = ord(goal) - ord('A') + 1
nrings  = math.ceil(math.sqrt(nchars))
nrings  = 1 + math.floor( nrings / 2 )
nlayers = 2 * nrings - 1
alpha   = lambda x: chr(ord('A')+x-1) if x <= nchars else ' '

for i in range(nlayers):
    print( ' '.join( alpha(x) for x in layer(i, nrings)) )