class Solution {
    public String countAndSay(int n) {
        if (n <= 0) return "-1";
        String ans = "1";

        for (int i = 1; i < n; i++){
            ans = build(ans);
        }

        return ans;
    }

    private String build(String str){
        StringBuilder sb = new StringBuilder();

        int p = 0;
        while (p < str.length()){
            char c = str.charAt(p);
            int count = 0;
            while (p < str.length() && str.charAt(p) == c){
                count++;
                p++;
            }
            sb.append(String.valueOf(count));
            sb.append(c);
        }

        return sb.toString();
    }
}