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

#define NMAX 103

char v[NMAX][NMAX];
int dp[NMAX][NMAX],ok[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");
    }

    if(v[1][1])
        ok[1][1]=1;

    for(i=1;i<=n;++i)
        for(j=1;j<=m;++j)
            if(v[i][j]=='.')
            {
                if(ok[i-1][j])
                {
                    dp[i][j]=dp[i-1][j];
                    ok[i][j]=1;
                }
                if(ok[i][j-1])
                {
                    dp[i][j]=max(dp[i][j],dp[i][j-1]);
                    ok[i][j]=1;
                }
                ++dp[i][j];

                if(dp[i][j]>sol)
                    sol=dp[i][j];
            }

    printf("%d\n",sol);
    return 0;
}