#include <fstream>
#include <iostream>

int main() {
	int N, M;

	std::ifstream fin("flip.in");
	std::ofstream fout("flip.out");

	fin >> N >> M;

	int i, j;
	int tabla[16][16];

	for (i = 0; i < N; ++i) {
		for (j = 0; j < M; ++j)
			fin >> tabla[i][j];
	}

	fin.close();

	for (i = 0; i < N; ++i)
		tabla[i][1] *= -1;

	for (j = 0; j < M; ++j)
		tabla[2][j] *= -1;

	int suma = 0;

	for (i = 0; i < N; ++i) {
		for (j = 0; j < M; ++j)
			suma += tabla[i][j];
	}

	fout << suma;
	fout.close();
}