#include <iostream>
#include <cstdio>
using namespace std;
#define N_MAX 105
char A[N_MAX][N_MAX];
short int B[N_MAX][N_MAX];
int n, m;
int main() {
    //freopen("input", "r", stdin);
    //freopen("output", "w", stdout);

    scanf("%d%d\n", &n, &m);
    for (int i = 1; i <= n; i++) {
        fgets(A[i] + 1, N_MAX - 1, stdin);
    }
    for (int i = 0; i <= max(n, m); i++) {
        B[i][0] = B[0][i] = -200;
    }
    int sol = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            B[i][j] = -200;
        }
    }
    B[1][1] = (A[1][1] == '.');
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (A[i][j] != '.') {
                continue;
            }
            if (A[i-1][j] == '.' && B[i-1][j] + 1 > B[i][j]) {
                B[i][j] = B[i-1][j] + 1;
            }
            if (A[i][j-1] == '.' && B[i][j-1] + 1 > B[i][j]) {
                B[i][j] = B[i][j-1] + 1;
            }
            if (B[i][j] > sol) sol = B[i][j];
        }
    }
    printf("%d\n", sol);
    return 0;
}