#include "stdio.h"
void main()
{
   char s[256];
   int i=0;
   printf("请输入一行字符，之后按回车键\n");
   gets(s);
   while(s[i]!=0)
   {
    if(s[i]>=65 && s[i]<=87)  /*A - W*/
    {
     s[i]=s[i]+3;
     i++;
     continue;
    }
    if(s[i]>=88 && s[i]<=90)   /* X,Y,Z */
    {
      s[i]=s[i]+3-26;
      i++;
      continue;
     }
    if(s[i]>=97 && s[i]<=119)  /*a - w*/
    {
      s[i]=s[i]+3;
       i++;
       continue;
     }
    if(s[i]>=120 && s[i]<=122)  /* x,y,z*/
     {
      s[i]=s[i]+3-26;
       i++;
       continue;
     }
     i++;
   }
   puts("\n"); puts(s);
}

#include "stdio.h"
void main()
{
   char s[256];
   int i=-1;
   printf("请输入一行字符，之后按回车键\n");
   gets(s);
   while(s[++i]!=0)
   {
    if(s[i]>=65 && s[i]<=87)  /*A - W*/
    {
     s[i]=s[i]+3;
     continue;
    }
    if(s[i]>=88 && s[i]<=90)   /* X,Y,Z */
    {
      s[i]=s[i]+3-26;
      continue;
     }
    if(s[i]>=97 && s[i]<=119)  /*a - w*/
    {
      s[i]=s[i]+3;
      continue;
     }
    if(s[i]>=120 && s[i]<=122)  /* x,y,z*/
     {
      s[i]=s[i]+3-26;
      continue;
     }
   }   puts("\n");   puts(s);
}

#include "stdio.h"
void main()
{
   char s[256];
   int i=-1;
   printf("请输入一行字符，之后按回车键\n");
   gets(s);
   while(s[++i]!=0)
   {
     if(s[i]>=65 && s[i]<=90)  /*A - Z*/
     {
      s[i]=(s[i]-65+3)%26+65;
      continue;
     }
     if(s[i]>=97 && s[i]<=122)  /*a - z*/
     {
       s[i]=(s[i]-97+3)%26+97;
       continue;
      }
   }   puts("\n");   puts(s);
}