说明：  2) 编程接受用户输入的一段英文文字，使用一个数组统计每个字母（不计大小写）出现的次数相对于字母总数的比率，打印显示这个比率。并对字母出现的比率进行排序。
(2) a program that accepts user input English text, using an array of statistics for each letter (ignoring case) relative to the number of occurrences of the ratio of the total number of letters, print, display this ratio. And the ratio of the letters appears to be sorted.)