#include<bits/stdc++.h>
#define N 1001
using namespace std;
int main()
{
	int n;
	string str;
	map<string,bool> m;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>str;
		m[str]=1;
	}
	int ans=0;
	map<string,bool>::iterator it;
	for(it=m.begin();it!=m.end();it++)
	{
		str.clear();
		for(int i=0;i<it->first.size();i++)
		{
			str+=it->first[i];
			if(!m[str])
				m[str]=1;
			else
			{
				if(i==(it->first.size()-1))
					continue;
				ans=max(ans,i+1);
			}
		}
	}
	printf("%d\n",ans);
	return 0;
}
/**************************************************************
	Problem: 1763
	User: admin
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2084 kb
****************************************************************/