#include<iostream>
using namespace std;
int main()
{
    int a[101][101]={0},n,m,i,j,mm=0;
    char ch;
   cin>>n>>m;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
    {
        cin>>ch;
        if(ch=='.')
            a[i][j]=1;
        else
            a[i][j]=0;
    }
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
        if(a[i][j]==1)
        {
            if(i==1)
            a[i][j]+=a[i][j-1];
            else
            a[i][j]+=max(a[i][j-1],a[i-1][j]);
            mm=max(mm,a[i][j]);
        }
       cout<<mm<<endl;
    return 0;
}