#include <bits/stdc++.h>
#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
#include<string>
using ll = long long;
using namespace std;

int main()
{
    ll n, m, max1 = 0;
    cin >> n >> m;
    vector<vector<ll>> s(n, vector<ll>(m));
    for (ll i = 0; i < n; i++) {
        string yn;
        cin >> yn;
        for (ll j = 0; j < m; j++) {
            if (yn[j] == 'x') s[i][j]++;
        }
    }
    for (ll i = 0; i < m; i++){
        ll sum1 = 0;
        for (ll j = 0; j < n; j++){
            sum1 += s[j][i];
        }
        max1 = max(max1, sum1);
    }
    cout << max1 + 1 << endl;
}