Cipher (+3)

#include "stdafx.h"
#include <iostream>
#include <string>

int main()
{
    std::string str;
    std::getline(std::cin, str);

    for(int index = 0; index < str.length(); index++){
        str[index] = tolower(str[index]) + 3;

        if(str[index] > 122){
            str[index] = tolower(str[index]) - 26;
        }
    }

    std::cout << str;

    return 0;
}