#include <stdio.h>
#include <queue>
#define nmax 101

using namespace std;

int sol[nmax][nmax];
queue < pair <int, int> > q;

int main()
{
    int N, M;
    scanf ("%d %d", &N, &M);
    int A[nmax][nmax], i, j, x, y, max;
    char c;
    for (i = 1; i <= N; ++i) {
        scanf ("%c", &c);
        for (j = 1; j <= M; ++j) {
            scanf ("%c", &c);
            if (c == '.') A[i][j] = 0;
            else A[i][j] = 1;
        }
    }
    for (i = 0; i <= N + 1; ++i)
        A[i][0] = 1, A[i][M+1] = 1;
    for (j = 0; j <= M + 1; ++j)
        A[0][j] = 1, A[N+1][j] = 1;
    q.push(make_pair(1,1));
    max = 1;
    sol[1][1] = 1;
    while (!q.empty()) {
        x = q.front().first;
        y = q.front().second;
        q.pop();
        if (A[x+1][y] == 0 && sol[x+1][y] < sol[x][y] + 1) {
            sol[x+1][y] = sol[x][y] + 1;
            q.push(make_pair(x+1,y));
            if (sol[x+1][y] > max)
                max = sol[x+1][y];
        }
        if (A[x][y+1] == 0 && sol[x][y+1] < sol[x][y] + 1) {
            sol[x][y+1] = sol[x][y] + 1;
            q.push(make_pair(x,y+1));
            if (sol[x][y+1] > max)
                max = sol[x][y+1];
        }
    }
    //if (A[1][1] == 1)
      //  max = 0;
    printf ("%d", max);
    return 0;
}