#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N, M;
	cin >> N >> M;
	vector<string> S( N );
	for( int i = 0; i < N; i++ ) cin >> S[i];

	vector<int> k( M );
	for( int i = 0; i < N; i++ ) {
		for( int j = 0; j < M; j++ ) {
			if( S[i][j] == 'x' ) k[j]++;
		}
	}
	int ans = 0;
	for( int i = 0; i < M; i++ ) ans = max( ans, k[i] );
	ans++;

	cout << ans << endl;
}