#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;
    }
}

bitset<1000> v[1000];
ll n;
inline void a(ll r,ll c){
    v[r][c].flip();
    v[r][(c-1+n)%n].flip();
    v[(r-1+n)%n][c].flip();
    v[(r-1+n)%n][(c-1+n)%n].flip();
}
inline void b(ll r,ll c){
    a(r,c);
    a(r,0);
    a(0,c);
}
inline void sa(ll r,ll c,set<pll> &st){
    st.insert({r,c});
    st.insert({(r-1+n)%n,c});
    st.insert({r,(c-1+n)%n});
    st.insert({(r-1+n)%n,(c-1+n)%n});
}
inline int sb(ll r,ll c){
    set<pll> st;
    sa(r,c,st);
    sa(r,0,st);
    sa(0,c,st);
    ll ret=0;
    for(auto [i,j]:st) ret+=v[i][j];
    return ret;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n;
    ll pre_score=0;
    rep(i,n){
        rep(j,n){
            char c;
            cin >> c;
            if(c=='#'){
                v[i][j]=1;
                pre_score++;
            }
        }
    }
    vector<vector<ll>> f(n,vector<ll>(n,0));
    mt19937 mt;
    while(true){
        ll ms=timer::get();
        if(1900<=ms) break;
        ll i=mt()%n,j=mt()%n;
        f[i][j]^=1;
        ll x=sb(i,j);
        b(i,j);
        ll y=sb(i,j);
        ll new_score=pre_score-x+y;
        double temp=4.0+(0.1-4.0)*(double)ms/1900.0;
        double prob=exp((double)(pre_score-new_score)/temp);
        if(1.0*mt()/mt19937::max()<prob){
            pre_score=new_score;
        }else{
            f[i][j]^=1;
            b(i,j);
        }
        if(pre_score==0) break;
    }
    if(pre_score!=0){
        cout << "-1\n";
    }else{
        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);
    }
}