#include <iostream>
#include <fstream>
using namespace std;

ifstream f("date.in");

int n, m;
char a[105][105];
int dp[105][105];

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> (a[i] + 1);
    }

    int mx = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (a[i][j] == '&') {
                dp[i][j] = 0;
                continue;
            }
            dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]) + 1;
            mx = max(mx, dp[i][j]);
        }
    }
    cout << mx << endl;

    return 0;
}