memo

　21ではなく、23だという話。
　http://www.google.co.jp/search?q=%E5%AE%89%E7%94%B0%E5%A5%BD%E5%BC%98+%E8%B6%B3%E7%AB%8B%E4%BF%AE%E4%B8%80+%E4%BB%8A%E6%9E%9D%E4%BB%81+%E6%9D%BE%E4%BA%95%E6%AD%A6+%E6%9C%AC%E7%94%B0%E5%85%86%E5%8F%B8+%E9%88%B4%E6%9C%A8%E6%B3%89+%E9%96%A2%E5%8E%9F%E5%8B%87+%E5%85%AB%E5%B0%8B%E5%85%89%E7%A7%80+%E9%AB%98%E6%9D%91%E6%98%AF%E6%87%BF+%E6%9C%AC%E5%A4%9A%E4%BF%8A%E4%B9%8B+%E5%A4%A7%E9%87%8E%E8%B2%B4%E9%9B%84+%E6%B5%85%E4%BA%95%E5%97%A3%E5%A4%AB+%E9%9D%92%E6%9C%A8%E5%AD%9D+%E4%BA%95%E4%B8%8A%E6%98%8E%E5%BD%A6+%E6%9D%91%E4%B8%8A%E6%BA%80%E5%BC%98+%E6%96%B0%E5%B7%9D%E7%99%BB%E8%8C%82%E5%AE%A3+%E5%B1%B1%E5%B4%8E%E5%90%89%E7%94%B7+%E5%8C%97%E6%BD%9F%E8%B0%B7%E4%BB%81+%E5%A4%A7%E6%B2%B3%E5%86%85%E7%A7%80%E6%98%8E+%E5%B0%8F%E6%9E%97%E4%BF%AE+%E6%B2%B3%E4%BA%95%E5%8C%A1%E7%A7%80+%E5%B1%B1%E7%94%B0%E5%BB%B6%E5%BA%83+%E6%96%B0%E8%B0%B7%E6%A1%82