else {
        if (m % 2 == 0) {
            int h = (n - 1)*m ;
            for (q = m; q; q--)
                cout << 1 << " " << q << endl;
            for (int xx = 2, yy = 1, u = 1; h; xx += u,h--) {
                cout << xx << " " << yy << endl;
                if (xx == n || (xx == 2 && yy > 1)) {
                    u *= -1;
                    yy++;
                    if (yy <= m) {
                        h--;
                        cout << xx << " " << yy << endl;
                    }
                }
            }
        }
        else if (n % 2 == 0) {
            int h = (m - 1)*n;
            for (q = n; q; q--)
                cout << q << " " << 1 << endl;
            for (int xx = 1, yy = 2, u = 1; h;h--, yy += u) {
                cout << xx << " " << yy << endl;
                if (yy == m || (yy == 2 && xx > 1)) {
                    u *= -1;
                    xx++;
                    if (xx <= n) {
                        h--;
                        cout << xx << " " << yy << endl;
                    }
                }
            }
        }
        else cout << -1;
    }