C++ :

#include<iostream>
#include<cstring>
using namespace std;
char s[100000];
int main()
{
	cin.getline(s,100000);
	int lon=strlen(s);
	for (int i=0; i<lon; i++)
	{
		if ((s[i]>='a'&&s[i]<='z') || (s[i]>='A'&&s[i]<='Z'))
		{
			s[i]+=4;
			if (s[i]>'Z' && s[i]<='Z'+4 || s[i]>'z')
				s[i]-=26;
		}
		cout<<s[i];
	}
	cout<<endl;
	return 0;
}