#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, m;
  cin >> n >> m;
  vector<string> s(n);
  rep(i, n) cin >> s[i];
  int ans = 0;
  rep(i, m) {
    int cnt = 0;
    rep(j, n) if (s[j][i] == 'x') cnt++;
    ans = max(ans, cnt + 1);
  }
  cout << ans << endl;
  return 0;
}