#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
#include <queue>
#include <map>
#include <cmath>
#include <iomanip>
#include <set>
#include <cstdio>
#include <string>

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];
  }
  int ans = 0;
  for (int i = 0; i < m; i++) {
    int cnt = 0;
    for (int j = 0; j < n; j++) {
      cnt += s[j][i] == 'x';
    }
    ans = max(ans, cnt);
  }
  cout << ans + 1 << endl;
  return 0;
}