#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;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll n;
    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;
        }
    }
    if(n==1){
        if(v[0][0]){
            cout << "-1\n";
        }else{
            cout << "1\n";
            cout << "0 0\n";
        }
        return 0;
    }else if(n==2){
        if((v[0][0]+v[0][1]+v[1][0]+v[1][1])==0){
            cout << "0\n";
        }else if((v[0][0]+v[0][1]+v[1][0]+v[1][1])==4){
            cout << "1\n";
            cout << "0 0\n";
        }else{
            cout << "-1\n";
        }
        return 0;
    }

    vector<vector<ll>> f(n,vector<ll>(n,0));

    auto a=[&](ll r,ll c){
        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;
    };
    auto b=[&](ll r,ll c){
        a(r,c);
        a(r,0);
        a(0,c);
        f[r][c]^=1;
    };

    
    replr(i,1,n){
        replr(j,1,n){
            if(!v[i-1][j-1]) continue;
            b(i,j);
        }
    }
    replr(i,1,n){
        if(!v[i-1][0]) continue;
        replr(j,1,n) b(i,j);
    }
    replr(j,1,n){
        if(!v[0][j-1]) continue;
        replr(i,1,n) b(i,j);
    }
    if(v[0][0]) b(0,0);
    rep(i,n){
        rep(j,n){
            if(v[i][j]){
                cout << "-1\n";
                return 0;
            }
        }
    }
    vector<pll> ans;
    rep(i,n){
        rep(j,n){
            if(f[i][j]) ans.emplace_back(i,j);
        }
    }
    cout << len(ans) << '\n';
    for(auto [l,r]:ans) cout << l << ' ' << r << '\n';
}