class Solution {
    public char kthCharacter(int k) {
        StringBuilder sb = new StringBuilder();
        sb.append('a');
        while(k > sb.length() - 1){
            int len = sb.length();
            for(int i = 0; i < len; i ++ ){
                sb.append((char)(sb.charAt(i) + 1));
            }
        }

        return sb.charAt(k - 1);
    }
}