static int[] dc = {-1, 1, 0, 0};

static int[] dr = {0, 0, -1, 1};

static int N;

public static void main(String[] args) throws IOException {

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

StringTokenizer st = new StringTokenizer(br.readLine());

N = Integer.parseInt(st.nextToken());

ArrayList<String>[] board = new ArrayList[N];

for (int i = 0; i < N; i++) {

String candy = br.readLine();

board[i] = new ArrayList<>();

for (int j = 0; j < N; j++) {

board[i].add(String.valueOf(candy.charAt(j)));

}

}

int total = 0;

for (int i = 0; i < N; i++) {

for (int j = 0; j < N; j++) {

int cc = 0;

int cr = 0;

for (int k = 0; k < 4; k++) {

cc = i + dc[k];

cr = j + dr[k];

if (!(0 > cc || cc >= N || 0 > cr || cr >= N)) {

if (!(board[cc].get(cr).equals(board[i].get(j)))) {

String tmp = board[cc].get(cr);

String Nowtmp = board[i].get(j);

board[i].set(j, tmp);

board[cc].set(cr, Nowtmp);

total = Integer.max(total,CountCandy(board));

board[i].set(j, Nowtmp);

board[cc].set(cr, tmp);

}

}

}

}

}

System.out.println(total);

}

public static int CountCandy(ArrayList<String>[] board) {

int maxRow = -(int) 1e9;

int maxCol = -(int) 1e9;

int totalMax;

for (int i = 0; i < N; i++) {

int rowCnt = 1;

int colCnt = 1;

for (int j = 0; j < N - 1; j++) {

if (board[i].get(j).equals(board[i].get(j + 1))) {

rowCnt += 1;

} else {

rowCnt = 1;

}

if (board[j + 1].get(i).equals(board[j].get(i))) {

colCnt += 1;

} else {

colCnt = 1;

}

maxRow = Integer.max(maxRow, rowCnt);

maxCol = Integer.max(maxCol, colCnt);

}

}

totalMax = Integer.max(maxRow, maxCol);

return totalMax;

}