#include<cstdio>
#include<vector>
#include<cmath>
#include<cstdlib>
#include<ctime>
#include<cstring>
#include<queue>
using namespace std;
int i,j,maxi,n,m,dp[109][109];
char a[109][109];
int max(int a,int b)
{
    if(a>b) return a;
    return b;
}
int main()
{
//freopen("input","r",stdin);
//freopen("output","w",stdout);
scanf("%d%d\n",&n,&m);
for(i=1;i<=n;i++)
    gets(a[i]+1);
for(i=0;i<=n;i++)
    for(j=0;j<=n;j++)
        dp[i][j]=-10000000;
dp[1][1]=1;
for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
if(i!=1||j!=1)
{        if(a[i][j]=='.') dp[i][j]=max(dp[i-1][j],dp[i][j-1])+1;
maxi=max(maxi,dp[i][j]);
}
printf("%d\n",maxi);
return 0;
}