import java.util.Arrays;

class Solution {
    public boolean solution(String[] phone_book) {
       Arrays.sort(phone_book);

        int size = phone_book.length;
        
        for (int i = 0; i < size - 1; i++) {
            String phoneNum = phone_book[i];
            String compareNum = phone_book[i + 1];

            if (compareNum.startsWith(phoneNum)) {
                return false;
            }
        }

        return true;
    }
}