#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;

int dp[1005][1005];
char str[1005][1005];

int main()
{
    int n;
    while(scanf("%d",&n)==1 && n)
    {
        for(int i=0; i<n; i++)
            scanf("%s",str[i]);
        memset(dp,0,sizeof(dp));
        int t1,t2,ans=1;;
        for(int i=0; i<n; i++)
        {
            for(int j=0; j<n; j++)
            {
                if(i==0 || j==n-1)    ///初始化
                    dp[i][j]=1;
                t1=i,t2=j;
                while(t1>=0 && t2<n && str[i][t2]==str[t1][j])
                {
                    t1--;
                    t2++;
                }
                t1=i-t1;
                if(t1>=dp[i-1][j+1]+1) dp[i][j]=dp[i-1][j+1]+1;
                else dp[i][j]=t1;
                ans=max(ans,dp[i][j]);
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}