#include <bits/stdc++.h>
/**
 3
 A B B
 A B A
 B A B
 */
using namespace std;
const int N = 110;
typedef pair<int, int> PII;
char a[N][N], b[N][N];
int n;
int dx[] = {-1, 0, 1, 0}; //上右下左
int dy[] = {0, 1, 0, -1}; //上右下左
int res;

void bfs(int x, int y) {
    memcpy(b, a, sizeof a);

    queue<PII> q;
    int cnt = 0;
    // b[x][y] = 'A';
    q.push({x, y});

    while (q.size()) {
        auto t = q.front();
        q.pop();
        cnt++;
        for (int i = 0; i < 4; i++) {
            int tx = t.first + dx[i], ty = t.second + dy[i];
            if (tx == 0 || tx > n || ty == 0 || ty > n) continue;
            if (b[tx][ty] == 'A') {
                b[tx][ty] = 'B';
                q.push({tx, ty});
            }
        }
    }
    res = max(res, cnt);
}
int main() {
    cin >> n;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            cin >> a[i][j];

    //每个b牌
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            if (a[i][j] == 'B')
                bfs(i, j);

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