#include <stdio.h>
#define MAXIM(a, b) (((a) < (b)) ? (b) : (a))

void adunare_main();
void cmmdc_main();
void filip_main();

int main() {
	filip_main();
	return 0;
}

void filip_main() {
    freopen("filip.in", "r", stdin);
    freopen("filip.out", "w", stdout);
    int i, j;
    int n, m, k;
    static int data[16][16];

    long sumLin, sumCol, result;

    scanf("%d %d\n", &n, &m);

    for (i = 0; i < n; i++) {
    	for (j = 0; j < m; j++) {
    		scanf("%d ", &data[i][j]);
    	}
    }

    for (i = 0; i < n; i++) {
		sumLin = 0;
		for (k = 0; k < m; k++)
			sumLin += data[i][k];
		if (sumLin < 0) {
			for (k = 0; k < m; k++)
				data[i][k] *= -1;
		}
    }

   	for (j = 0; j < m; j++) {
   		sumCol = 0;
   		for (k = 0; k < n; k++)
   			sumCol += data[k][j];
		if (sumCol < 0) {
			for (k = 0; k < n; k++)
				data[k][j] *= -1;
		}
   	}

    result = 0;
    for (i = 0; i < n; i++) {
    	for (j = 0; j < m; j++) {
    		result += data[i][j];
    	}
    }
    printf("%ld\n", result);
}

void adunare_main() {
    freopen("adunare.in", "r", stdin);
    freopen("adunare.out", "w", stdout);

	long long a, b;
	scanf("%lld\n%lld", &a, &b);
	printf("%lld\n", a + b);
}

int cmmdc(int a, int b) {
	if (a == 1 || b == 1)
		return 0;
	if (a == b)
		return a;
	if (a > b)
		return cmmdc(a - b, b);
	return cmmdc(a, b - a);
}

void cmmdc_main() {
    freopen("cmmdc.in", "r", stdin);
    freopen("cmmdc.out", "w", stdout);
    int a, b;
    scanf("%d %d\n", &a, &b);
	printf("%d\n", cmmdc(a, b));
}