#include <stdio.h>

 #include <algorithm>

 #include <string.h>

 using namespace std;

 const int N =  + ;

 char s[N][N];

 int dp[N][N];

 int n;

 int main()

 {

     while(scanf("%d",&n) ==  && n)

     {

         for(int i=;i<=n;i++) scanf("%s",s[i]+);

         int ans = ;

         for(int i=;i<=n;i++)

         {

             for(int j=n;j>=;j--)

             {

                 dp[i][j] = ;

                 if(i ==  || j == n) continue;

                 int lim = dp[i-][j+];

                 for(int k=;k<=lim;k++)

                 {

                     if(s[i-k][j] == s[i][j+k]) dp[i][j]++;

                     else break;

                 }

                 ans = max(ans, dp[i][j]);

             }

         }

         printf("%d\n",ans);

     }

     return ;

 }