Phone Number

Time Limit: 1000 ms Memory Limit: 65536 KiB

Problem Description

We know that if a phone number A is another phone number B’s prefix, B is not able to be called. For an example, A is 123 while B is 12345, after pressing 123, we call A, and not able to call B.
Given N phone numbers, your task is to find whether there exits two numbers A and B that A is B’s prefix.

Input

 The input consists of several test cases.
 The first line of input in each test case contains one integer N (0<N<1001), represent the number of phone numbers.
 The next line contains N integers, describing the phone numbers.
 The last case is followed by a line containing one zero.

Output

 For each test case, if there exits a phone number that cannot be called, print “NO”, otherwise print “YES” instead.

Sample Input

2
012
012345
2
12
012345
0

Sample Output

NO
YES

Hint

 

Source

2010年山东省第一届ACM大学生程序设计竞赛