C :

#include<stdio.h>
int main(){
char c;
  while((c=getchar())!='\n'){
    if(c>='A'&&c<='Z' || c>='a'&&c<='z'){
      if(c>='W'&&c<='Z' || c>='w'&&c<='z')
        c=c-26+4;
      else
        c=c+4;
    }
    printf("%c",c);
  }
  printf("\n");
  return 0;
}

C++ :

#include <stdio.h>
#include <math.h>
int main() {
	char c;
	while ((c = getchar()) != '\n') {
		if (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z')) {
			c = c + 4;
			if (c > 'Z' && c <= 'Z' + 4 || c > 'z')
				c = c - 26;
		}
		printf("%c", c);
	}
	printf("\n");
	return 0;
}

Pascal :

var
  i:longint;
  s,sa:string;
  c:char;

function turn(c:char):char;
var ch:char;
begin
  ch:=upcase(c);
  ch:=chr( (ord(ch)-ord('A')+4) mod 26 + ord('A') );
  if(upcase(c)=c) then exit(ch)
    else exit(lowercase(ch));
end;

begin
  readln(s);
  sa:='';
  for i:=1 to length(s) do begin
    c:=upcase(s[i]);
    if( c in ['A'..'Z'] ) then sa:=sa+turn(s[i])
      else sa:=sa+s[i];
  end;
  writeln(sa);
end.

Java :

import java.util.*;
public class Main {
    public static void main(String args[]) {
        Scanner cin = new Scanner(System.in);
        String s = cin.nextLine();
        char[] c = s.toCharArray();
        for(int i=0;i<c.length;i++){
            if((c[i]>='A' && c[i]<='Z')||(c[i]>='a' && c[i]<='z'))
            {
                c[i]+=4;
                if((c[i]>'Z'&&c[i]<'a')||c[i]>'z')
                    c[i]-=26;
            }
        }
        System.out.println(new String(c));
    }
}

Python :

from string import maketrans
table = maketrans('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', 'efghijklmnopqrstuvwxyzabcdEFGHIJKLMNOPQRSTUVWXYZABCD')
print raw_input().translate(table)