#include <fstream>

using namespace std;

ifstream fin ("mesaj4.in");
ofstream fout ("mesaj4.out");

int N, M, x, y;

int main() {
	fin >> N >> M >> x >> y;

	fout << -1 << "\n";
//	for(int i = 1; i <= 2*(N-1); ++i) {
//		fout << x << " " << y << "\n";
//	}

}