B

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    int n, m;
    cin>>n>>m;

    vector<string> s(n);
    for(auto &e: s)
      cin>>e;

    string t = "";

    for(int j=0; j<m; j++)
    {
        int f = 1;

        for(int i=0; i<n; i++)
            f &= (s[i][j] == 'o');

        if(f)       t += 'o';
        else        t += 'x';
    }

    int ans = 0;
    int val = 0;

    for(auto e: t)
    {
        if(e == 'o')        val++;
        else                val = 0;

        ans = max(ans, val);
    }

    cout<<ans<<"\n";
}