#include <algorithm>
#include <cstdio>

using namespace std;

char cit[200];
int dp[105][105];

int main()
{
    //freopen("input", "r", stdin);
    //freopen("output", "w", stdout);
    int n, m, i, j, sol=0;
    scanf("%d %d\n", &n, &m);
    dp[1][1]=1;
    for(i=1;i<=n;i++)
    {
        fgets(cit+1, 200, stdin);
        for(j=1;j<=m;j++)
        {
            if(cit[j]=='.')
            {
                if(dp[i-1][j]|| dp[i][j-1]) dp[i][j]=max(dp[i-1][j], dp[i][j-1])+1;
                sol=max(sol, dp[i][j]);
            }
        }
    }
    printf("%d", sol);
}