public class Solution {
    public String rot13(String text) {
        
        StringBuilder sb = new StringBuilder();

        for(int i = 0; i < text.length(); i++) {

            char c = text.charAt(i);

            if(c >= 'A' && c <= 'Z') {

                c = (char) ('A' + (c - 'A' + 13) % 26);

            } else if (c >= 'a' && c <= 'z') {

                c = (char) ('a' + (c - 'a' + 13) % 26);

            }

            sb.append(c);

        }
        return sb.toString();
    }
}