There are 50 numbers from 1 to 50 written on the paper. Xiaohong and Xiaofang play counting games. You can cross out any number at any time, but you must write down the single digit of the sum of the numbers that are crossed out. Repeat this operation until there is only one number left on the paper. Guess what is the last remaining number?
纸上写有1一50这50个数，小红和小方做划数的游戏，每次可以任意划去若干个数，但必须写下划去的几个数的和的个位数字．重复这样的操作，直到纸上只剩下一个数为止．猜最后剩下的数是多少？
<result>5</result>