#include<fstream>
using namespace std;
int n, m, i, j, ok1, ok2, L1, L2, C1, C2, ok;
pair<int, int> v1[501], v2[501];
int a1[501][501], a2[501][501];
ifstream fin("becuri.in");
ofstream fout("becuri.out");
int main(){
    fin>> n >> m;
    for(i = 1; i <= n; i++){
        for(j = 1; j <= m; j++){
            fin>> a1[i][j];
            a2[i][j] = a1[i][j];
        }
    }
    for(j = 1; j <= m; j++){
        a1[1][j] = 1 - a1[1][j];
    }
    L1 = 1;
    v1[1].first = 1;
    for(j = 1; j <= m; j++){
        if(a1[1][j] == 1){
            C1++;
            v1[C1].second = j;
            for(i = 1; i <= n; i++){
                a1[i][j] = 1- a1[i][j];
            }
        }
    }
    for(i = 2; i <= n; i++){
        ok = 1;
        for(j = 2; j <= m; j++){
            if(a1[i][j] != a1[i][j-1]){
                ok = 0;
                break;
            }
        }
        if(ok == 0){
            ok1 = 1;
            break;
        }
        else{
            if(a1[i][1] == 1){
                L1++;
                v1[L1].first = i;
            }
        }
    }
    if(L1 % 2 != C1 % 2){
        ok1 = 1;
    }

     for(j = 1; j <= m; j++){
        if(a2[1][j] == 1){
            C2++;
            v2[C2].second = j;
            for(i = 1; i <= n; i++){
                a2[i][j] = 1- a2[i][j];
            }
        }
    }
    for(i = 2; i <= n; i++){
        ok = 1;
        for(j = 2; j <= m; j++){
            if(a2[i][j] != a2[i][j-1]){
                ok = 0;
                break;
            }
        }
        if(ok == 0){
            ok2 = 1;
            break;
        }
        else{
            if(a2[i][1] == 1){
                L2++;
                v2[L2].first = i;
            }
        }
    }
    if(L2 % 2 != C2 % 2){
        ok2 = 1;
    }
    if(ok1 == 1 && ok2 == 1){
        fout<<"-1\n";
        return 0;
    }
    if(ok1 == 0 && ok2 == 0){
        if(max(L1, C1) < max(L2, C2)){
            fout<< max(L1, C1) <<"\n";
            for(i = 1; i <= min(L1, C1); i++){
                fout<< v1[i].first <<" "<< v1[i].second <<"\n";
            }
            if(L1 < C1){
                for(i = L1 + 1; i <= C1; i++){
                    fout<< v1[L1].first <<" "<< v1[i].second <<"\n";
                }
            }
            else{
                for(i = C1 + 1; i <= L1; i++){
                    fout<< v1[i].first <<" "<< v1[C1].second <<"\n";
                }
            }
        }
        else{
             fout<< max(L2, C2) <<"\n";
            for(i = 1; i <= min(L2, C2); i++){
                fout<< v2[i].first <<" "<< v2[i].second <<"\n";
            }
            if(L2 < C2){
                for(i = L2 + 1; i <= C2; i++){
                    fout<< v2[L2].first <<" "<< v2[i].second <<"\n";
                }
            }
            else{
                for(i = C2 + 1; i <= L2; i++){
                    fout<< v2[i].first <<" "<< v2[C1].second <<"\n";
                }
            }
        }
    }
    else{
        if(ok1 == 0){
             fout<< max(L1, C1) <<"\n";
            for(i = 1; i <= min(L1, C1); i++){
                fout<< v1[i].first <<" "<< v1[i].second <<"\n";
            }
            if(L1 < C1){
                for(i = L1 + 1; i <= C1; i++){
                    fout<< v1[L1].first <<" "<< v1[i].second <<"\n";
                }
            }
            else{
                for(i = C1 + 1; i <= L1; i++){
                    fout<< v1[i].first <<" "<< v1[C1].second <<"\n";
                }
            }
        }
        else{
            fout<< max(L2, C2) <<"\n";
            for(i = 1; i <= min(L2, C2); i++){
                fout<< v2[i].first <<" "<< v2[i].second <<"\n";
            }
            if(L2 < C2){
                for(i = L2 + 1; i <= C2; i++){
                    fout<< v2[L2].first <<" "<< v2[i].second <<"\n";
                }
            }
            else{
                for(i = C2 + 1; i <= L2; i++){
                    fout<< v2[i].first <<" "<< v2[C1].second <<"\n";
                }
            }
        }
    }
    return 0;
}