KINDS_OF_COIN = [500, 100, 50, 10, 5, 1]

puts "please input total yen."
total_yen = gets.chomp.to_i

hand_coins = Hash.new
used_coins = Hash.new

KINDS_OF_COIN.each do |kind_of_coin|
  print "please input the amount of each coin[#{kind_of_coin}] => "
  hand_coins[kind_of_coin] = gets.chomp.to_i

  # calc part
  used_coins[kind_of_coin] = total_yen / kind_of_coin
  if used_coins[kind_of_coin] > hand_coins[kind_of_coin]
    used_coins[kind_of_coin] = hand_coins[kind_of_coin]
  end
  puts "using #{kind_of_coin}: #{used_coins[kind_of_coin]}"

  total_yen -= kind_of_coin * used_coins[kind_of_coin]
end

puts "total using #{used_coins.values.inject(0) { |sum, i| sum + i }} coins."