#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#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;
  cin >> n;
  vector Grid(n, vector<char>(n));
  rep(i, n) rep(j, n) cin >> Grid[i][j];
  vector<pair<int, int>> id(0);
  for (int i = 0; i < n; ++i) {
    for (int j = i + 1; j < n; ++j) {
      id.push_back({ i, j });
    }
  }
  assert(id.size() <= 15);
  int ans = 1e9;
  rep(bit, 1 << id.size()) {
    bool ok = true;
    vector<int> cnt(n, 0);
    rep(i, id.size()) {
      auto [x, y] = id[i];
      if (bit & (1 << i)) {
        if (Grid[x][y] == 'o' || Grid[x][y] == '-')
          ++cnt[x];
        else
          ok = false;
      }
      else {
        if (Grid[x][y] == 'x' || Grid[x][y] == '-')
          ++cnt[y];
        else
          ok = false;
      }
    }
    if (ok) {
      set<int> st(cnt.begin(), cnt.end());
      map<int, int> mp;
      int cur = 0;
      for (auto x : st) mp[x] = cur++;
      ans = min(ans, cur - mp[cnt[0]]);
    }
  }
  cout << ans << endl;
  return 0;
}