#include <fstream>
#include <queue>
//run
using namespace std;
int a[102][102];

int main()
{
    int n, m, i, j;
    char c;
    fscanf(stdin,"%d %d", &n, &m);
    for (i = 0; i < n; ++i)
    {
        fscanf(stdin,"\n%c", &c);
        if (c == '.')
            a[i][0] = 0;
        else
            a[i][0] = -1;
        for (j = 1; j < m; ++j)
        {
            fscanf(stdin,"%c", &c);
            if (c == '.')
                a[i][j] = 0;
            else
                a[i][j] = -1;
        }
        a[i][j] = -1;
    }
    for (j = 0; j <= m; ++j)
        a[i][j] = -1;

    a[0][0] = 1;
    queue<int> b;
    queue<int> d;
    b.push(0);
    d.push(0);
    int maxim = 1;
    while (!b.empty())
    {
        i = b.front();
        j = d.front();
        b.pop();
        d.pop();
        if (a[i+1][j] == 0)
        {
            a[i+1][j] = a[i][j] + 1;
            b.push(i+1);
            d.push(j);
            if (maxim < a[i+1][j])
                maxim = a[i+1][j];
        }
        if (a[i][j+1] == 0)
        {
            a[i][j+1] = a[i][j] + 1;
            b.push(i);
            d.push(j+1);
            if (maxim < a[i+1][j])
                maxim = a[i+1][j];
        }
    }

    fprintf(stdout, "%d", maxim);
    return 0;
}