1400  Longest common prefix
Time Limit : 2 Second
Memory Limit : 128 MB
Submission: 722
Solved: 137
 Description
Given N string S[1], S[2]......, S[N], you are to find a pair of strings whose longest common prefix has the largest length.
 Input
There are multiple test cases. For each case:
The first line is a integer N. (2 <= N <= 20000)
The next N lines each contains a nonempty string S[i]. The length of S[i] is at most 50.
 Output
For each case output a line representing the length of longest common prefix.
 sample input

3 bcabc bcd abcd
 sample output

2
 hint
 source
 Xiaobin YANG