#include<iostream>
#include<fstream>
#define NN 109


using namespace std;

int a[NN][NN],n,m;




int main()
{

    cin >> n >> m;
    for(int i=1 ;i<=n ;i++)
        {

            for(int j=1 ; j<=m;j++)
            {

                char c;
                cin >> c;
                if ( c == '.')
                    a[i][j] = 0;
                else
                    a[i][j] = -1;
            }
        }


        for(int i=1;i<=m;i++)
            a[0][i] = -1;

        for(int i=1 ;i<=n ; i++)
            a[i][0] = -1;


        int maxx = 0;
        for(int i=1 ; i<=n ;i++)
            for(int j=1 ; j<=m ;j++)
                if( a[i][j] !=-1  )
            {
                a[i][j] = max(a[i-1][j] , a[i][j-1]) + 1;
                if(a[i][j] == 0 && (i + j) != 2)
                    a[i][j] = -1;
                if( a[i][j] > maxx )
                    maxx = a[i][j];
            }


    cout << maxx + 1;



    return 0;

}