#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<map>
#include<math.h>
#define all(x) x.begin(),x.end()
#define pb push_back
#define ll long long 
#define P pair<double,double>
#define LP pair<ll,ll>
using namespace std;
int main() {
	int n,m,ma=0;
	cin >>n>>m;
	vector<int> a(m);
	for (int i = 0; i < n; i++) {
		string s;
		cin >> s;
		for (int j = 0; j < m; j++) {
			if (s[j] == 'x') a[j] += 1;
			ma = max(ma, a[j]);
		}
	}
	cout << ma+1 << endl;
	return 0;
}