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

#define N 1100
#define MOD 1000000007
#define met(a, b) memset(a, b, sizeof(a))
#define INF 0x3f3f3f3f

char G[N][N];
int dp[N][N];

int main()
{
    int n;

    while(scanf("%d", &n), n)
    {
        int i, j, i1, j1, Max=1;

        met(G, 0);
        met(dp, 0);
        for(i=0; i<n; i++)
            scanf("%s", G[i]);

        for(i=0; i<n; i++)
        for(j=0; j<n; j++)
        {
            if(i==0 || j==n-1)
            {
                dp[i][j] = 1;
                continue;
            }
            i1=i, j1=j;
            while(j1<n && i1>=0 && G[i1][j]==G[i][j1] )
                 i1--, j1++;

            if((i-i1)>=dp[i-1][j+1]+1) dp[i][j] = dp[i-1][j+1] + 1;
            else dp[i][j] = i-i1;

            Max = max(Max, dp[i][j]);
        }

        printf("%d\n", Max);
    }
    return 0;
}