#!/usr/bin/python -Wall

# ================================================================
# Produces output as follows:
#
# bash$ tridiag 6 2 -1
#  2 -1  0  0  0  0
# -1  2 -1  0  0  0
#  0 -1  2 -1  0  0
#  0  0 -1  2 -1  0
#  0  0  0 -1  2 -1
#  0  0  0  0 -1  2
#
# John Kerl
# kerl.john.r@gmail.com
# 2006-05-26
# ================================================================
# This software is released under the terms of the GNU GPL.
# Please see LICENSE.txt in the same directory as this file.
# ================================================================

from __future__ import division # 1/2 = 0.5, not 0.
import sys
argc = len(sys.argv)
if (argc != 4):
	print >> sys.stderr, "Usage: ", sys.argv[0], "{n} {diag element} {off-diag element}"
	sys.exit(1)

n = int(sys.argv[1])
d = float(sys.argv[2])
u = float(sys.argv[3])

# Don't print decimal points for integer values.
id = int(d)
iu = int(u)
if (d == float(id)):
	d = id
if (u == float(iu)):
	u = iu

for i in range(0, n):
	for j in range(0, n):
		if (i == j):
			print d,
		elif (i == j-1):
			print u,
		elif (i == j+1):
			print u,
		else:
			print 0,
	print