#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ull=unsigned long long;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll,ll>;
using ld=long double;
const ll INF=(1ll<<60);
#define rep(i,n) for (ll i=0;i<(ll)(n);i++)
#define replr(i,l,r) for (ll i=(ll)(l);i<(ll)(r);i++)
#define all(v) v.begin(),v.end()
#define len(v) ((ll)v.size())
template<class T> inline bool chmin(T &a,T b){
    if(a>b){
        a=b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T &a,T b){
    if(a<b){
        a=b;
        return true;
    }
    return false;
}
namespace timer{
    auto start=chrono::system_clock::now();
    void snap(){
        start=chrono::system_clock::now();
    }
    int get(){
        auto now=chrono::system_clock::now();
        int ms=chrono::duration_cast<chrono::milliseconds>(now-start).count();
        return ms;
    }
}
ll n;
void a(ll r,ll c,vector<vector<ll>> &v){
    v[r][c]^=1;
    v[r][(c-1+n)%n]^=1;
    v[(r-1+n)%n][c]^=1;
    v[(r-1+n)%n][(c-1+n)%n]^=1;
}
void b(ll r,ll c,vector<vector<ll>> &v){
    a(r,c,v);
    a(r,0,v);
    a(0,c,v);
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n;
    vector<vector<ll>> v(n,vector<ll>(n,0));
    rep(i,n){
        rep(j,n){
            char c;
            cin >> c;
            if(c=='#') v[i][j]=1;
        }
    }
    vector<vector<ll>> hv=v;
    vector<ll> ord(n*n);
    rep(i,n*n) ord[i]=i;
    mt19937 mt;
    while(true){
        int ms=timer::get();
        if(1900<=ms) break;
        shuffle(all(ord),mt);
        vector<vector<ll>> f(n,vector<ll>(n,0));
        v=hv;
        while(true){
            int ms2=timer::get();
            if(1900<=ms2) break;
            bool ok=true,br=false;
            for(auto ij:ord){
                ll i=ij/n,j=ij%n;
                if(v[i][j]){
                    if(f[i][j]){
                        br=true;
                        break;
                    }
                    f[i][j]^=1;
                    b(i,j,v);
                    ok=false;
                }
            }
            if(br) break;
            if(ok){
                vector<pll> ans;
                rep(i,n){
                    rep(j,n){
                        if(f[i][j]) ans.emplace_back(i,j);
                    }
                }
                cout << len(ans) << '\n';
                for(auto [i,j]:ans){
                    cout << i << ' ' << j << '\n';
                }
                exit(0);
            }
        }
    }
    cout << "-1\n";
}