#include<stdio.h>
#include<algorithm>
using namespace std;

#define NMAX 103

char v[NMAX][NMAX];
int dp[NMAX][NMAX];

int main()
{
    //freopen("date.in","r",stdin);
    int n,m,i,j,sol=0;
    scanf("%d%d\n",&n,&m);


    for(i=1;i<=n;++i)
    {
        for(j=1;j<=m;++j)
            scanf("%c",&v[i][j]);
        scanf("\n");
    }

    for(i=1;i<=n;++i)
        for(j=1;j<=m;++j)
        {
            if(v[i][j]=='.')
                dp[i][j]=max(dp[i-1][j],dp[i][j-1])+1;
            if(dp[i][j]>sol)
                sol=dp[i][j];
        }
    printf("%d\n",sol);
    return 0;
}