#include <bits/stdc++.h>
using namespace std;
template <class T>
void splitstr(const string &s, vector<T> &out) {
  istringstream in(s);
  out.clear();
  copy(istream_iterator<T>(in), istream_iterator<T>(), back_inserter(out));
}
template <class T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
static void redirect(int argc, const char **argv) {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  if (argc > 1) {
    static filebuf f;
    f.open(argv[1], ios::in);
    cin.rdbuf(&f);
    if (!cin) {
      cerr << "Failed to open '" << argv[1] << "'" << endl;
      exit(1);
    }
  }
  if (argc > 2) {
    static filebuf f;
    f.open(argv[2], ios::out | ios::trunc);
    cout.rdbuf(&f);
    if (!cout) {
      cerr << "Failed to open '" << argv[2] << "'" << endl;
    }
  }
}
class UnionFind {
 private:
  mutable std::vector<int> parent;

 public:
  explicit UnionFind(int size = 0) : parent(size, -1) {}
  int size() const { return parent.size(); }
  int find(int x) const {
    assert(x >= 0 && x < size());
    int y = x;
    while (parent[y] >= 0) y = parent[y];
    while (parent[x] >= 0) {
      int nxt = parent[x];
      parent[x] = y;
      x = nxt;
    }
    return y;
  }
  bool merge(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return false;
    if (-parent[x] > -parent[y]) std::swap(x, y);
    parent[y] += parent[x];
    parent[x] = y;
    return true;
  }
  int component_size(int x) const { return -parent[find(x)]; }
};
template <typename T, typename C, T Modulus>
class MR {
 private:
  struct tag_plus {};
  struct tag_minus {};
  struct tag_good {};
  T value;
  static_assert(std::numeric_limits<C>::max() / Modulus / Modulus > 0,
                "compute type is too small");
  static_assert(Modulus < std::numeric_limits<T>::max() / 2,
                "storage type is too small");
  void reduce(tag_plus) {
    if (value >= Modulus) value -= Modulus;
  }
  void reduce(tag_minus) {
    if (value < 0) value += Modulus;
  }
  void reduce(tag_good) {}

 public:
  static const T modulus = Modulus;
  MR() : value(0) {}
  MR(C value) : value(value % Modulus) { reduce(tag_minus()); }
  template <typename tag_t>
  MR(T value, tag_t tag) : value(value) {
    reduce(tag);
  }
  MR &operator=(C value) {
    this->value = value % Modulus;
    reduce(tag_minus());
    return *this;
  }
  MR operator+(MR b) const { return MR(value + b.value, tag_plus()); }
  MR operator-(MR b) const { return MR(value - b.value, tag_minus()); }
  MR operator*(MR b) const {
    return MR(C(value) * C(b.value) % Modulus, tag_good());
  }
  MR operator-() const { return MR(-value, tag_minus()); }
  MR &operator+=(MR b) {
    value += b.value;
    reduce(tag_plus());
    return *this;
  }
  MR &operator-=(MR b) {
    value -= b.value;
    reduce(tag_minus());
    return *this;
  }
  MR &operator*=(MR b) {
    value = C(value) * C(b.value) % Modulus;
    return *this;
  }
  bool operator==(MR b) const { return value == b.value; }
  bool operator!=(MR b) const { return value != b.value; }
  T get() const { return value; }
};
static inline int bit(int x) { return 1 << x; }
static int min_colours(const vector<int> &edges) {
  int N = ((long long)(edges).size());
  int M = 1 << N;
  vector<MR<int, long long, 1000000009> > a(M);
  a[0] = 1;
  for (int i = 1; i < M; i++) {
    int v = __builtin_ctz(i);
    a[i] = a[i & ~bit(v)] + a[i & ~bit(v) & ~edges[v]];
  }
  vector<MR<int, long long, 1000000009> > ak(M,
                                             MR<int, long long, 1000000009>(1));
  for (int k = 1;; k++) {
    MR<int, long long, 1000000009> sum = 0;
    for (int i = 0; i < M; i++) {
      ak[i] *= a[i];
      sum += __builtin_parity(i) ? ak[i] : -ak[i];
    }
    if (sum.get() != 0) return k;
  }
}
int main(int argc, const char **argv) {
  redirect(argc, argv);
  int N;
  cin >> N;
  vector<string> matrix(N);
  UnionFind scc(N);
  for (int i = 0; i < N; i++) {
    cin >> matrix[i];
    for (int j = 0; j < i; j++)
      if (matrix[i][j] == 'A') scc.merge(i, j);
  }
  vector<pair<int, int> > comps;
  for (int i = 0; i < N; i++)
    if (i == scc.find(i)) comps.emplace_back(scc.component_size(i), i);
  sort(begin(comps), end(comps));
  reverse(begin(comps), end(comps));
  vector<int> cmap(N);
  int C = ((long long)(comps).size());
  int C2 = 0;
  while (C2 < C && comps[C2].first >= 2) C2++;
  for (int i = 0; i < C; i++) cmap[comps[i].second] = i;
  C = C2;
  vector<int> edge(C);
  for (int i = 0; i < N; i++)
    for (int j = 0; j < i; j++)
      if (matrix[i][j] == 'X') {
        int p = cmap[scc.find(i)];
        int q = cmap[scc.find(j)];
        if (p == q) {
          cout << "-1\n";
          return 0;
        }
        if (p < C && q < C) {
          edge[p] |= bit(q);
          edge[q] |= bit(p);
        }
      }
  int mc = C2 ? min_colours(edge) : 0;
  cout << N - 1 + mc << '\n';
  return 0;
}
