#include <iostream>
#include <fstream>

short N , M, a,b;
long long m[17][17], sum;

int main(){
	ifstream in("flip.in"); // take input
	ofstream out("flip.out"); // give output
	
	cin >> N >> M // dimensiumile matricei
	
	
	for(short i=0;i<N;i++){
		for(short j=0;j<M;j++){
			cin >> m[i][j];
		              }}
	for(short i=0;i<N;i++){
		a=0;b=0;
		for(short j=o;j<M;++j){
			a+=m[j][i];
			b+=-1*m[j][i];
			}
				
			if(a<b)
			for(short x=0;x<N;x++)
					m[x][i]= -1*m[x][i];
			} a =0;b =0;
	for(short z=0;z<N;++z){
		a=0;b=0;		
             for(short c=0;c<M;c++){
			a+=m[z][c];
			b+=-1*m[z][c];
			}
			if(b>a)
			for(short x=0;x<M;x++)
					m[z][c] = -1*m[z][c];
	} a=0;b=0;
	for(;a<N;a++){
		for(;b<M;b++){
			sum += m[a][b];
	}} cout << sum;	
	


}