我也不知道第7个点为什么会RE

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.InputStreamReader;

class SC{
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer tokenizer = new StringTokenizer("");
    public String next() throws Exception{
        while(!tokenizer.hasMoreTokens()){
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
    public int nextInt() throws Exception{
        return Integer.parseInt(next());
    }
}
public class Main {
    static int n;
    static int N = 500010;
    static int[][] son = new int[N][26];
    static int[] cnt = new int[N];
    static int idx = 0;
    static int max = 0;
    static SC sc = new SC();
    static ArrayList<String> list = new ArrayList<>();
    static void insert(String s){
        int p = 0;
        int num = 0;
        for(int i = 0;i < s.length();i ++){
            int u = s.charAt(i) - 'a';
            if(son[p][u] == 0) son[p][u] = ++ idx;
            p = son[p][u];
            if(cnt[p] != 0)
                num ++;
        }
        cnt[p] ++;
        max = Math.max(num,max);
    }
    public static void main(String[] args) throws Exception {
        n = sc.nextInt();
        while(n -- > 0){
            String s = sc.next();
            list.add(s);
        }
        Comparator<String> comparator = new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                return o1.length() - o2.length();
            }
        };
        Collections.sort(list,comparator);
        for(String str : list){
            insert(str);
        }
        System.out.println(max + 1);
    }
}