#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<string> s(n);
  rep(i, n) cin >> s[i];
  rep(i, n) rep(j, n) s[i][j] = s[i][j] == '#';
  vector<vector<char>> act(n, vector<char>(n));
  auto do_op = [&](int i, int j) {
    rep(di, 2) rep(dj, 2) {
      int x = i - di, y = j - dj;
      x %= n, y %= n;
      if (x < 0) x += n;
      if (y < 0) y += n;
      s[x][y] ^= 1;
    }
  };
  auto do_act = [&](int i, int j) {
    i %= n, j %= n;
    if (i < 0) i += n;
    if (j < 0) j += n;
    act[i][j] ^= 1;
    do_op(i, j);
    do_op(i, 0);
    do_op(0, j);
  };
  auto do_act4 = [&](int i, int j) {
    rep(di, 2) rep(dj, 2) do_act(i - di, j - dj);
  };
  if (n % 2 == 0) {
    bool acc = 0;
    for (int j = 0; j < n; j += 2) acc ^= s[0][j];
    if (acc) do_act(0, 0);
    for (int i = n - 1; i >= 2; i--) {
      for (int j = n - 1; j >= 2; j--) {
        if (s[i][j]) do_act4(i, j);
      }
    }
  } else {
    for (int i = (n + n - 2) % n; i != 0; i = (n + i - 2) % n) {
      for (int j = (n + n - 2) % n; j != 0; j = (n + j - 2) % n) {
        if (s[i][j]) do_act4(i, j);
      }
    }
  }
  vector<P> ans;
  rep(i, n) rep(j, n) {
    if (s[i][j]) {
      cout << -1 << '\n';
      return 0;
    }
    if (act[i][j]) ans.emplace_back(i, j);
  }
  cout << ans.size() << '\n';
  for (auto [i, j] : ans) cout << i << ' ' << j << '\n';
}