DEBUG = true MOD = 10**9+7 def main _N = int mat = rep(_N) { [nil] * _N } _N.times do |n| i, j = n, n n += 1 _N.times do i = (i + 1) % _N j = (j - 1) % _N mat[i][j] = n end end mat.each do |row| puts row.join(" ") end end def int; gets.to_i; end def ints; gets.split.map &:to_i; end def string; gets.chomp; end def rep(n, &b); n.times.map(&b); end def yes; puts "Yes"; end def no; puts "No"; end def yesno t; t ? Yes : No; end def debug(x); STDERR.puts x.inspect if DEBUG; end def debug_grid(grid, size=8); grid.each { |row| STDERR.puts row.map { |x| x.inspect.ljust(size) }.join(" ") } if DEBUG; end def factorial(n, mod); (2..n).inject(1) { |f, x| f * x % mod }; end def cumsum(xs); ys = [0]; xs.each { |x| ys << x + ys[-1] }; ys; end def cumdiff(ys); xs = []; xs.inject { |x, y| xs << (d = y - x); d }; end def mod_inv(x, mod); x.pow(mod-2, mod); end def mod_div(x, y, mod); x * mod_inv(y, mod) % mod; end main