#include <iostream>
#include <bits/stdc++.h>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
int n, m, a[20][20];
int main()
{
    fin >> n >> m;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            fin >> a[i][j];
    /// verificam liniile
    for(int i=1;i<=n;i++)
    {
        int sum=0, sum_neg = 0;
        for(int j=1;j<=m;j++)
        {
            sum+= a[i][j];
            sum_neg+= -1*a[i][j];
        }
        if(abs(sum_neg) > sum)
            for(int j=1;j<=n;j++)
                a[i][j] = -1*a[i][j];
    }
    /// verificam coloanele
    for(int j=1;j<=m;j++)
        {
            int sum = 0, sum_neg = 0;
            for(int i=1;i<=n;i++)
            {
                sum+= a[i][j];
                sum_neg += -1*a[i][j];
            }
            if(abs(sum_neg) > sum)
                for(int i=1;i<=n;i++)
                    a[i][j]*=-1;
        }
    int s = 0;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            s+= a[i][j];
    fout << s;
    return 0;
}