#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <string.h>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <time.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <deque>

using namespace std;

const char infile[] = "input.in";
const char outfile[] = "output.out";

ifstream fin(infile);
ofstream fout(outfile);

const int MAXN = 105;
const int oo = 0x3f3f3f3f;

typedef vector<int> Graph[MAXN];
typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

int N, M, dp[MAXN][MAXN];
char s[MAXN][MAXN];

int main() {
    int Ans = 1;
    cin >> N >> M;
    memset(dp, -oo, sizeof(dp));
    dp[0][0] = dp[1][0] = 0;
    dp[1][1] = 1;
    for(int i = 1 ; i <= N ; ++ i)
        cin >> (s[i] + 1);
    for(int i = 1 ; i <= N ; ++ i) {
        for(int j = 1 ; j <= M ; ++ j) {
            if(s[i][j] == '.') {
                dp[i][j] = max(dp[i-1][j], dp[i][j - 1]) + 1;
                Ans = max(Ans, dp[i][j]);
            }
            //cout << dp[i][j] << ' ';
        }
        //cout << "\n";
    }
    cout << Ans << '\n';
    fin.close();
    fout.close();
    return 0;
}