#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N;
int A[1010][1010];
int R[1010],C[1010];
vector<pair<int,int>> V;

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N;
	FOR(y,N) {
		cin>>s;
		FOR(x,N) if(s[x]=='#') {
			A[y][x]=1;
			R[y]^=1;
			C[x]^=1;
		}
	}
	FOR(i,N) {
		if(R[i]||C[i]) {
			cout<<-1<<endl;
			return;
		}
		R[i]=C[i]=0;
	}
	
	if(N==1) {
		cout<<0<<endl;
		return;
	}
	N--;
	
	FOR(y,N) FOR(x,N) {
		if(y) A[y][x]^=A[y-1][x];
		if(x) A[y][x]^=A[y][x-1];
		if(y&&x) A[y][x]^=A[y-1][x-1];
		if(A[y][x]) R[y]^=1,C[x]^=1;
	}
	
	if(N%2) {
		FOR(i,N) if(R[0]!=R[i]||R[0]!=C[i]) break;
		if(i<N) {
			cout<<-2<<endl;
			return;
		}
	}
	
	FOR(y,N) FOR(x,N) if(A[y][x]^R[y]^C[x]) V.push_back({y,x});
	cout<<V.size()<<endl;
	FORR2(y,x,V) cout<<y+1<<" "<<x+1<<endl;
	
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}