[문제요약]하나의 문자열이 주어질 때 두 번이상 나오는 가장 긴 스트링의 크기를 구하는 문제.

sabcabcfabc , sabcabcfabc , sabcabcfabc

trutrutiktiktappop , trutrutiktiktappop 

As Ivana is running late, Zvonko has been looking at the screen for a while and noticed that some messages appeared on the screen more than once. Naturally, he's been writing down all messages on a piece of paper. He wants to know the length of the longest string that appeared at least twice (appears in two different positions on the paper).

입력

• The first line of input contains an integer L (1 ≤ L ≤ 200 000), the length of the string Zvonko wrote down.
• The second line contains a string of L lowercase letter of the English alphabet.

출력

입출력 예

input 

11 
sabcabcfabc 

output 

3 

input 

18 
trutrutiktiktappop 

output 

4

input 

6 
abcdef 

output 

0

출처:coci/2006-2007/contest5 6