#include <fstream>
#define MAX 20
using namespace std;

int a[MAX][MAX];
int n, m, j, i;
int sum, suma;

ofstream fout("flip.out");

void Read();
void Solve();

int main()
{
    Read();
    Solve();
    
    return 0;
}

void Read()
{
    ifstream fin("flip.in");
    fin >> m >> n;
    for(i = 1; i <= m; i++)
        for(j = 1; j <= n; j++)
        {
            fin >> a[i][j];
        }
    fin.close();
}

void Solve()
{
    for(i = 1; i <= m; i++)
        for(j = 1; j <= n; j++)
        {
            do
            {
                 sum += a[i][1];
                 suma += a[i][j];
                 if(sum < 0)
                 {
                        if(suma > sum)
                        {
                            sum = sum;
                        }      
                        else
                        {
                            sum *= -1;
                        }    
                }
                else
                {
                       if(suma < sum)
                       {
                          sum = sum;
                       }
                       else
                       {
                          sum *= -1;
                       }
               }
               break;
           }while(i == m && j == n);    
        }
        if(sum < suma)  fout << suma;
        else            fout << sum;
        fout.close();
}