//#define NDEBUG
#pragma warning(disable : 4146)

#include <bits/stdc++.h>

namespace n91 {

  using i32 = std::int32_t;
  using i64 = std::int64_t;
  using u32 = std::uint32_t;
  using u64 = std::uint64_t;
  using isize = std::ptrdiff_t;
  using usize = std::size_t;
  using f64 = double;

#ifdef _MSC_VER
  using i128 = i64;
  using u128 = u64;
#else
  using i128 = __int128_t;
  using u128 = __uint128_t;
#endif

  struct rep {
    struct itr {
      usize i;
      constexpr itr(const usize i) noexcept : i(i) {}
      void operator++() noexcept { ++i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    const itr f, l;
    constexpr rep(const usize f, const usize l) noexcept
      : f(std::min(f, l)), l(l) {}
    constexpr auto begin() const noexcept { return f; }
    constexpr auto end() const noexcept { return l; }
  };
  struct revrep {
    struct itr {
      usize i;
      constexpr itr(const usize i) noexcept : i(i) {}
      void operator++() noexcept { --i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    const itr f, l;
    constexpr revrep(const usize f, const usize l) noexcept
      : f(l - 1), l(std::min(f, l) - 1) {}
    constexpr auto begin() const noexcept { return f; }
    constexpr auto end() const noexcept { return l; }
  };
  template <class T> auto md_vec(const usize n, const T& value) {
    return std::vector<T>(n, value);
  }
  template <class... Args> auto md_vec(const usize n, Args... args) {
    return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
  }
  template <class T> constexpr T difference(const T& a, const T& b) noexcept {
    return a < b ? b - a : a - b;
  }
  template <class T> void chmin(T& a, const T& b) noexcept {
    if (b < a)
      a = b;
  }
  template <class T> void chmax(T& a, const T& b) noexcept {
    if (a < b)
      a = b;
  }
  template <class F> class rec_lambda {
    F f;

  public:
    rec_lambda(F&& f_) : f(std::forward<F>(f_)) {}
    template <class... Args> auto operator()(Args &&... args) const {
      return f(*this, std::forward<Args>(args)...);
    }
  };
  template <class T> T scan() {
    T ret;
    std::cin >> ret;
    return ret;
  }
  constexpr char eoln = '\n';

  i64 floor_div(const i64 n, const i64 d) {
    assert(d != 0);
    return n / d - static_cast<i64>((n ^ d) < 0 && n % d != 0);
  }

  i64 ceil_div(const i64 n, const i64 d) {
    assert(d != 0);
    return n / d + static_cast<i64>((n ^ d) >= 0 && n % d != 0);
  }

#ifdef N91_LOCAL
#define OJ_LOCAL(a, b) b
#else
#define OJ_LOCAL(a, b) a
#endif

} // namespace n91

#include <atcoder/modint>
using mint = atcoder::modint998244353;

namespace n91 {

  void main_() {
    const usize n = scan<usize>();
    std::vector<std::string> s(n);
    for (auto& e : s)
      std::cin >> e;
    const char fl = '.' ^ '#';
    const auto move = [&](const usize r, const usize c) {
      s[r][c] ^= fl;
      s[r][(c ? c : n) - 1] ^= fl;
      s[(r ? r : n) - 1][c] ^= fl;
      s[(r ? r : n) - 1][(c ? c : n) - 1] ^= fl;
    };
    auto ans = md_vec(n, n, u32(0));
    const auto act = [&](const usize r, const usize c) {
      move(r, c);
      move(r, 0);
      move(0, c);
      ans[r][c] ^= 1;
    };
    const auto output = [&] {
      bool ok = true;
      for (const auto& r : s) {
        for (const auto& e : r) {
          if (e == '#')
            ok = false;
        }
      }
      if (ok) {
        std::vector<std::pair<usize, usize>> res;
        for (const usize i : rep(0, n)) {
          for (const usize j : rep(0, n)) {
            if (ans[i][j]) {
              res.push_back({ i, j });
            }
          }
        }
        std::cout << res.size() << eoln;
        for (const auto& [i, j] : res) {
          std::cout << i << " " << j << "\n";
        }
      }
      else {
        std::cout << "-1" << eoln;
      }
    };

    if (n == 1) {
      output();
      return;
    }

    if (s[n - 1][n - 1] == '#')
      act(0, 0);
    for (const usize i : revrep(1, n - 1)) {
      for (const usize j : revrep(1, n - 1)) {
        if (s[i][j] == '#')
          act(i, j);
      }
    }
    if (n % 2 == 0) {
      output();
    }
    else {
      for (const usize i : revrep(1, n)) {
        if (s[i][0] == '#') {
          for (const usize j : rep(0, n)) {
            act(i, j);
          }
        }
      }
      for (const usize j : revrep(1, n)) {
        if (s[0][j] == '#') {
          for (const usize i : rep(0, n)) {
            act(i, j);
          }
        }
      }
      output();
    }
  }

} // namespace n91

int main() {
  //*
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  //*/
  std::cout << std::fixed << std::setprecision(20);
  n91::main_();
  return 0;
}