package main

import (
    "io"
    "os"
    "strings"
)

type rot13Reader struct {  
    r io.Reader
}

func rot13(out byte) byte{  //字母转换
    switch{
        case out >= 'A' && out <= 'M' || out >= 'a' && out <= 'm':
            out += 13
        case out >= 'N' && out <= 'Z' || out >= 'n' && out <= 'z':
            out -= 13
    }        
    return out
}    
    
func (fz rot13Reader) Read(b []byte) (int,error){  //重写Read方法
    n, e := fz.r.Read(b)
           for i := 0; i < n; i++ {
        b[i] = rot13(b[i])    
        }            
    return n,e
}