#include <bits/stdc++.h>

using namespace std;

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

int n, m, S = 0;
int V[17][17];

void Read()
{
    fin >> n >> m;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            fin >> V[i][j];
}

void Flip(int lc, int i)
{
    if(lc == 1)
        for(int j = 1; j <= n; ++j)
            V[j][i] *= -1;
    else
        for(int j = 1; j <= m; ++j)
            V[i][j] *= -1;
}

void Solve()
{
    int sumL, sumC;
    for(int i = 1; i <= n; ++i)
    {
        sumL = sumC = 0;
        for(int j = 1; j <= m; ++j)
        {
            sumL += V[i][j];
            sumC += V[j][i];
        }
        if(sumL < 0)
            Flip(0,i);
        if(sumC < 0)
            Flip(1,i);
    }
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            S += V[i][j];
}

int main()
{
    Read();
    Solve();
    fout << S;
    return 0;
}