#!/usr/bin/env ruby # -*- coding: utf-8 -*- def kuku(kakerareru, kakeru) if kakerareru < 0 || kakeru < 0 return nil end return kakeru*kakerareru end puts "九九の計算をします。" print "かけられる数を入力:" suzi1 = gets.to_i print "かける数を入力:" suzi2 = gets.to_i printf("解答は%dです。\n", kuku(suzi1, suzi2))