#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

int main() {
    ll N;
    cin >> N;
    vector<string> S(N);
    for (ll i = 0; i < N; i++) {
        cin >> S[i];
    }
    vector<ll> rows(N, 0);
    vector<ll> cols(N, 0);
    for (ll i = 0; i < N; i++) {
        for (ll j = 0; j < N; j++) {
            if (S[i][j] == '#') {
                rows[i]++;
                cols[j]++;
            }
        }
    }
    for (ll i = 0; i < N; i++) {
        if (rows[i] % 2 == 1) {
            cout << -1 << endl;
            return 0;
        }
        if (cols[i] % 2 == 1) {
            cout << -1 << endl;
            return 0;
        }
    }
    vector<vector<ll>> sums(N + 1, vector<ll>(N + 1, 0));
    for (ll i = 0; i < N; i++) {
        for (ll j = 0; j < N; j++) {
            if (S[i][j] == '#') {
                sums[i + 1][j + 1] += 1;
            }
            sums[i + 1][j + 1] +=
                (sums[i + 1][j] + sums[i][j + 1] - sums[i][j] + 2) % 2;
            sums[i + 1][j + 1] %= 2;
        }
    }
    vector<ll> rows2(N - 1);
    vector<ll> cols2(N - 1);
    for (ll i = 1; i < N; i++) {
        for (ll j = 1; j < N; j++) {
            if (sums[i][j] == 1) {
                rows2[i - 1] += 1;
                cols2[j - 1] += 1;
                rows2[i - 1] %= 2;
                cols2[j - 1] %= 2;
            }
        }
    }
    if (N % 2 == 1) {
        vector<pll> ans(0);
        for (ll i = 1; i < N; i++) {
            for (ll j = 1; j < N; j++) {
                if ((rows2[i - 1] + cols2[j - 1] + 2 - sums[i][j]) % 2 == 1) {
                    ans.push_back(pll(i, j));
                }
            }
        }
        ll len = ans.size();
        cout << len << endl;
        for (ll i = 0; i < len; i++) {
            cout << ans[i].first << " " << ans[i].second << endl;
        }
    } else {
        bool all_odd = true;
        bool all_even = true;
        for (ll i = 0; i < N - 1; i++) {
            if (rows2[i] % 2 == 1 || cols2[i] % 2 == 1) {
                all_even = false;
            }
            if (rows2[i] % 2 == 0 || cols2[i] % 2 == 0) {
                all_odd = false;
            }
        }
        if (!all_odd && !all_even) {
            cout << -1 << endl;
        } else {
            vector<pll> ans(0);
            for (ll i = 1; i < N; i++) {
                for (ll j = 1; j < N; j++) {
                    if (sums[i][j] == 1) {
                        ans.push_back(pll(i, j));
                    }
                }
            }
            ll len = ans.size();
            cout << len << endl;
            for (ll i = 0; i < len; i++) {
                cout << ans[i].first << " " << ans[i].second << endl;
            }
        }
    }
}