#include <iostream>
#define DIM 101

using namespace std;

int main()
{
    short n,m;
    char c;
    int a[DIM][DIM],mx=1,b[DIM][DIM];
    cin>>n>>m;
    for(short i=1;i<=n;++i)
    for(short j=1;j<=m;++j)
    {
        cin>>c;
        if(c=='.')
        a[i][j]=0;
        else
        a[i][j]=-1;
    }
    b[1][1]=1;
    int i=2;
    while(a[1][i]==0 && i<=m)
    {
        b[1][i]=b[1][i-1]+1;
        ++i;
    }
    if(b[1][i-1]>mx)
    mx=b[1][i-1];
    i=2;
    while(a[i][1]==0 && i<=n)
    {
        b[i][1]=b[i-1][1]+1;
        ++i;
    }
    if(b[i-1][1]>mx)
    mx=b[i-1][1];
    for(short i=2;i<=n;++i)
    {
        for(short j=2;j<=m;++j)
        {
            if(a[i][j]!=-1 && (b[i-1][j]>0 || b[i][j-1]>0))
            {
                b[i][j]=max(b[i-1][j], b[i][j-1])+1;
                if(b[i][j]>mx)
                mx=b[i][j];
            }
        }
    }
    cout<<mx;
    return 0;
}