public class Solution {
    public static String largestString(String s) {
        char[] chars = s.toCharArray();
        int len = chars.length;
        StringBuilder cur = new StringBuilder();

        for (int i = len - 1; i >= 0; i--) {
            cur.insert(0, chars[i]);

            if (cur.length() == 3) {
                if (cur.toString().equals("abb")) {
                    chars[i] = 'b';
                    chars[i + 1] = 'a';
                    chars[i + 2] = 'a';
                    if (i + 4 < len && chars[i + 4] == 'b') {
                        i += 4 + 1;
                    } else if (i + 3 < len && chars[i + 3] == 'b') {
                        i += 3 + 1;
                    } else if (chars[i + 2] == 'b') {
                        i += 2 + 1;
                    }
                }
                if (chars[i + 1] == 'b') {
                    i += 1 + 1;
                } else {
                    ++i;
                }
                cur.setLength(0);
            }
        }

        return new String(chars);
    }
}