#include <bits/stdc++.h>
const int mod = 1000000007;
const int gmod = 3;
const int inf = 1039074182;
const double eps = 1e-9;
const long long llinf = 2LL * inf * inf;
template <typename T1, typename T2>
inline void chmin(T1 &x, T2 b) {
  if (b < x) x = b;
}
template <typename T1, typename T2>
inline void chmax(T1 &x, T2 b) {
  if (b > x) x = b;
}
inline void chadd(int &x, int b) {
  x += b - mod;
  x += (x >> 31 & mod);
}
template <typename T1, typename T2>
inline void chadd(T1 &x, T2 b) {
  x += b;
  if (x >= mod) x -= mod;
}
template <typename T1, typename T2>
inline void chmul(T1 &x, T2 b) {
  x = 1LL * x * b % mod;
}
template <typename T1, typename T2>
inline void chmod(T1 &x, T2 b) {
  x %= b, x += b;
  if (x >= b) x -= b;
}
template <typename T>
inline T mabs(T x) {
  return (x < 0 ? -x : x);
}
using namespace std;
using namespace std;
template <typename T>
ostream &operator<<(ostream &cout, vector<T> vec) {
  cout << "{";
  for (int i = 0; i < (int)vec.size(); i++) {
    cout << vec[i];
    if (i != (int)vec.size() - 1) cout << ',';
  }
  cout << "}";
  return cout;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &cout, pair<T1, T2> p) {
  cout << "(" << p.first << ',' << p.second << ")";
  return cout;
}
template <typename T, typename T2>
ostream &operator<<(ostream &cout, set<T, T2> s) {
  vector<T> t;
  for (auto x : s) t.push_back(x);
  cout << t;
  return cout;
}
template <typename T, typename T2>
ostream &operator<<(ostream &cout, multiset<T, T2> s) {
  vector<T> t;
  for (auto x : s) t.push_back(x);
  cout << t;
  return cout;
}
template <typename T>
ostream &operator<<(ostream &cout, queue<T> q) {
  vector<T> t;
  while (q.size()) {
    t.push_back(q.front());
    q.pop();
  }
  cout << t;
  return cout;
}
template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &cout, map<T1, T2, T3> m) {
  for (auto &x : m) {
    cout << "Key: " << x.first << ' ' << "Value: " << x.second << endl;
  }
  return cout;
}
template <typename T1, typename T2>
void operator+=(pair<T1, T2> &x, const pair<T1, T2> y) {
  x.first += y.first;
  x.second += y.second;
}
template <typename T1, typename T2>
pair<T1, T2> operator+(const pair<T1, T2> &x, const pair<T1, T2> &y) {
  return make_pair(x.first + y.first, x.second + y.second);
}
template <typename T1, typename T2>
pair<T1, T2> operator-(const pair<T1, T2> &x, const pair<T1, T2> &y) {
  return make_pair(x.first - y.first, x.second - y.second);
}
template <typename T1, typename T2>
pair<T1, T2> operator-(pair<T1, T2> x) {
  return make_pair(-x.first, -x.second);
}
template <typename T>
vector<vector<T>> operator~(vector<vector<T>> vec) {
  vector<vector<T>> v;
  int n = vec.size(), m = vec[0].size();
  v.resize(m);
  for (int i = 0; i < m; i++) {
    v[i].resize(n);
  }
  for (int i = 0; i < m; i++) {
    for (int j = 0; j < n; j++) {
      v[i][j] = vec[j][i];
    }
  }
  return v;
}
void print0x(int x) {
  std::vector<int> vec;
  while (x) {
    vec.push_back(x & 1);
    x >>= 1;
  }
  std::reverse(vec.begin(), vec.end());
  for (int i = 0; i < (int)vec.size(); i++) {
    std::cout << vec[i];
  }
  std::cout << ' ';
}
template <typename T>
void print0x(T x, int len) {
  std::vector<int> vec;
  while (x) {
    vec.push_back(x & 1);
    x >>= 1;
  }
  reverse(vec.begin(), vec.end());
  for (int i = (int)vec.size(); i < len; i++) {
    putchar('0');
  }
  for (size_t i = 0; i < vec.size(); i++) {
    std::cout << vec[i];
  }
  std::cout << ' ';
}
vector<string> vec_splitter(string s) {
  s += ',';
  vector<string> res;
  while (!s.empty()) {
    res.push_back(s.substr(0, s.find(',')));
    s = s.substr(s.find(',') + 1);
  }
  return res;
}
void debug_out(vector<string> __attribute__((unused)) args,
               __attribute__((unused)) int idx,
               __attribute__((unused)) int LINE_NUM) {
  cerr << endl;
}
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
  if (idx > 0)
    cerr << ", ";
  else
    cerr << "Line(" << LINE_NUM << ") ";
  stringstream ss;
  ss << H;
  cerr << args[idx] << " = " << ss.str();
  debug_out(args, idx + 1, LINE_NUM, T...);
}
struct DSUAE {
  int *f;
  inline void clear(int n) {
    for (int i = 0; i < n; i++) {
      f[i] = i;
    }
  }
  inline void init(int n) {
    f = new int[n + 5];
    clear(n);
  }
  inline int find(int x) { return (f[x] == x ? x : f[x] = find(f[x])); }
  inline void merge(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return;
    if (x & 1)
      f[x] = y;
    else
      f[y] = x;
  }
};
struct DSU {
  int *f;
  int *depth;
  int *sz;
  inline void clear(int n) {
    for (int i = 0; i < n; i++) {
      f[i] = i;
      depth[i] = 1;
      sz[i] = 1;
    }
  }
  inline void init(int n) {
    f = new int[n + 5];
    depth = new int[n + 5];
    sz = new int[n + 5];
    clear(n);
  }
  inline int find(int x) { return (f[x] == x ? x : f[x] = find(f[x])); }
  inline int getSize(int x) { return sz[find(x)]; }
  inline int merge(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return false;
    if (depth[x] > depth[y]) {
      f[y] = x;
      sz[x] += sz[y];
    } else if (depth[y] > depth[x]) {
      f[x] = y;
      sz[y] += sz[x];
    } else {
      sz[y] += sz[x];
      f[x] = y;
      depth[y]++;
    }
    return true;
  }
  inline int same(int x, int y) { return (find(x) == find(y)); }
  ~DSU() {
    delete f;
    delete depth;
    delete sz;
  }
};
struct PersistentDSU : public DSU {
  int find(int x) { return (x == f[x] ? x : find(f[x])); }
  inline int merge(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return false;
    if (depth[x] > depth[y]) {
      f[y] = x;
      sz[x] += sz[y];
    } else if (depth[y] > depth[x]) {
      f[x] = y;
      sz[y] += sz[x];
    } else {
      sz[y] += sz[x];
      f[x] = y;
      depth[y]++;
    }
    return true;
  }
};
using namespace std;
int n;
char c[55][55];
DSUAE dsu;
vector<int> scc[55];
vector<vector<int>> a;
int b[55][55];
int p[55];
int main() {
  double t = clock();
  scanf("%d", &n);
  dsu.init(n);
  for (int i = 0; i < n; i++) scanf("%s", c[i]);
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (c[i][j] == 'A') dsu.merge(i, j);
    }
  }
  for (int i = 0; i < n; i++) scc[dsu.find(i)].push_back(i);
  int now = 0;
  for (int i = 0; i < n; i++) {
    if (scc[i].empty()) continue;
    for (auto x : scc[i]) {
      for (auto y : scc[i]) {
        if (c[x][y] == 'X') {
          cout << "-1" << endl;
          exit(0);
        };
      }
    }
    if (scc[i].size() > 1)
      now += scc[i].size();
    else
      now += 1;
    if (scc[i].size() > 1) a.push_back(scc[i]);
  }
  n = a.size();
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (i == j) continue;
      bool noXor = true;
      for (auto x : a[i]) {
        for (auto y : a[j]) {
          noXor &= (c[x][y] != 'X');
        }
      }
      if (!noXor)
        b[i][j] = 1;
      else
        b[i][j] = 0;
    }
  }
  for (int i = 0; i < n; i++) p[i] = i;
  int res = inf;
  while ((clock() - t) / CLOCKS_PER_SEC <= 0.001) {
    random_shuffle(p, p + n);
    vector<vector<int>> v;
    for (int i = 0; i < n; i++) {
      int x = p[i];
      int found = false;
      for (auto &vv : v) {
        int ok = true;
        for (auto &u : vv) {
          ok &= (b[u][x] == 0);
        }
        if (ok) {
          found = true;
          vv.push_back(x);
          break;
        }
      }
      if (!found) {
        v.push_back(vector<int>{x});
      }
    }
    chmin(res, v.size());
  }
  cout << res + now - 1 << endl;
  return 0;
}
