N, M = gets.split.map(&:to_i)
A = gets.split.map(&:to_i)

counter = A.map { |a| a % M }.tally
counter.default = 0

ans = 0

0.upto(M / 2) do |i|
  j = M - i

  ans += [counter[i], counter[j]].max
end

puts ans