#include <iostream>
#include <fstream>

using namespace std;


int main() {
	ifstream fin("flip.in");
	ofstream fout("flip.out");

	int N, M;

	fin >> N >> M;

	int v[10][16];

	for (int i = 0; i < N; i++) {
		for (int j = 0; j < M; j++)
			fin >> v[i][j];
	}
		
	for (int i = 0; i < N; i++)
		v[i][1] *= -1;

	for (int i = 0; i < M; i++)
		v[2][i] *= -1;

	int sum = 0;

	for (int i = 0; i < N; i++) {
		for (int j = 0; j < M; j++)
			sum += v[i][j];
	}

	fout << sum;

	return 0;
}