#include <stdio.h>

#define MAX 16

int suma_l(int tab[MAX][MAX], int max, int lin) {
	int i, suma = 0;
	for(i=0; i<max; i++) 
		suma += tab[lin][i];
	return suma;
}

int suma_c(int tab[MAX][MAX], int max, int col) {
	int i, suma = 0;
	for(i=0; i<max; i++) 
		suma += tab[i][col];
	return suma;
}

void invert_l(int tab[MAX][MAX], int max, int lin) {
	int i;
	for(i=0; i<max; i++)
		tab[lin][i] = tab[lin][i] * -1;
}

void invert_c(int tab[MAX][MAX], int max, int col) {
	int i;
	for(i=0; i<max; i++)
		tab[i][col] = tab[i][col] * -1;
}

void print_tab(int tab[MAX][MAX], int maxl, int maxc) {
	int i, j;
	for (i=0; i<maxl; i++) {
		for(j=0; j<maxc; j++)
			printf("%4d", tab[i][j]);
		printf("\n");
	}
	printf("\n");
}

void read_Flip(int tab[MAX][MAX], int *N, int *M, char *filename) {
	int i,j;
	FILE *f1 = fopen(filename, "r");

	fscanf(f1, "%d", N);
	fscanf(f1, "%d", M);
	
	//printf("N=%d; M=%d\n", *N, *M);
	
	for(i=0; i<*N; i++)
		for(j=0; j<*M; j++)
			fscanf(f1, "%d", &tab[i][j]);
			
	//print_tab(tab, *N, *M);

	fclose(f1);	
}

int suma_tot(int tab[MAX][MAX], int n, int m) {
	int i, suma=0;
	for(i=0; i<n; i++)
		suma += suma_l(tab, m, i);
	return suma;
}

void write_suma(int suma, char *filename) {
	FILE *f2 = fopen(filename, "w");
	fprintf(f2, "%d\n", suma);
	fclose(f2);
}


void copy(int Flip[MAX][MAX], int F[MAX][MAX], int N, int M) {
	int i, j;
	for (i=0; i<N; i++)
		for(j=0; j<M; j++)
			F[i][j] = Flip[i][j];
}

int verify_each(int Flip[MAX][MAX], int N, int M, int imin, int jmin, int max) {
	int i,j;
	int suma1, change = 0, suma2;
	
	//printf("imin=%d   jmin=%d     MAX = %d\n", imin, jmin, max);
	//print_tab(Flip, N, M);
	
	int max_tmp = suma_tot(Flip, N, M);
	if(max > max_tmp)
		max_tmp = max;
	
	//printf("max_tmp = %d\n", max_tmp);
	
	if(imin<N) {
		int F[MAX][MAX];
		copy(Flip, F, N, M);
		invert_l(F, M, imin);
		suma1 = verify_each(F, N, M, imin+1, jmin, max_tmp);
		if(suma1>max_tmp)
			max_tmp = suma1;
		//printf("max_tmp = %d ---- imin=%d\n", max_tmp, imin);
		suma1 = verify_each(Flip, N, M, imin+1, jmin, max_tmp);
		if(suma1>max_tmp)
			max_tmp = suma1;
		//printf("max_tmp = %d ---- imin=%d\n", max_tmp, imin);
	}
	if(jmin<M) {
		int G[MAX][MAX];
		copy(Flip, G, N, M);
		invert_c(G, N, jmin);
		//invert_c(Flip, N, jmin);
		suma2 = verify_each(G, N, M, imin, jmin+1, max_tmp);
		if(suma2>max_tmp)
			max_tmp = suma2;
			
		//printf("max_tmp j = %d\n", max_tmp);
	suma2 = verify_each(Flip, N, M, imin, jmin+1, max_tmp);
		if(suma2>max_tmp)
			max_tmp = suma2;
			
		//printf("max_tmp j = %d\n", max_tmp);
	}
	/*
	if(imin<N && jmin<M) {
		int H[MAX][MAX];
		copy(Flip, H, N, M);
		invert_c(H, N, jmin);
		invert_l(H, M, imin);
		suma2 = verify_each(H, N, M, imin+1, jmin+1, max_tmp);
		if(suma2>max_tmp)
			max_tmp = suma2;
			
		//printf("max_tmp j = %d\n", max_tmp);
	}*/
	return max_tmp;
}

int main() {

	int N, M, suma, change;
	int Flip[MAX][MAX];
	
	read_Flip(Flip, &N, &M, "flip.in");
	
	change = suma_tot(Flip, N, M);
	suma = verify_each(Flip, N, M, 0, 0, change);

	write_suma(suma, "flip.out");

	return 0;	
}