Cifrul lui Cezar(criptarea şi decriptarea unui cuvânt)

#include<iostream>
using namespace std;
int main()
{char s[100],*p;
int n;
cin.get(s,100);
cin>>n;
strupr(s);
for(p=s;*p;p++)
    if(isalpha(*p))
        *p=(*p-'A'+n)%26+'A';

cout<<s<<endl;

for(p=s;*p;p++)
    if(isalpha(*p))
        *p=(*p-'A'+26-n)%26+'A';

cout<<s;
}