#include<stdio.h>
#include<string.h>
int main(){char a[100]="ABCabc";int i=0;for(i=0;i<strlen(a);i++){if(a[i]>='x'&&a[i]<='z' || a[i]>='X'&&a[i]<='Z'){a[i]=a[i]-26+3;}else{a[i]=a[i]+3;}}puts(a);
}

运行结果：