#include <iostream>
#include <fstream>
using namespace std;

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

int main(){
    int N, M, i, j, sum, tabla[17][17]; 
    
    fin >> N >> M;
    
    //CITIRE TABLA
    for(i = 1; i <= N; i++){
        sum = 0;
        for(j = 1; j <= M; j++){
            fin >> tabla[i][j];
            sum += tabla[i][j];
        }
        if(sum < 0 )
            for(j = 1; j <= M; j++)
                tabla[i][j] = tabla[i][j] * -1;
    }   

    //PRELUCRARE TABLA
    for(j = 1; j <= M; j++){
        sum = 0;
        for(i = 1; i <= N; i++)
            sum += tabla[i][j];
        if(sum < 0) 
               for(i = 1; i <= N; i++)
                    tabla[i][j] *= -1;
    }

    sum = 0;
    for(i = 1; i <= N; i++)
        for(j = 1; j <= M; j++)
            sum += tabla[i][j];
    
    fout << sum;
   
    return 0;
}