#include <stdio.h>
#include <vector>
#include <algorithm>
#define min 1000000

using namespace std;

int N,M,t[17][17];
struct p
{
   int x,y;
};
long mini,REZ=0;
p mink;
vector <long> found;

void _read()
{
 freopen("flip.in","r",stdin);
 freopen("flip.out","w",stdout);

 scanf("%d %d",&N,&M);

 for(int i=0;i<N;i++)
  for(int j=0;j<M;j++)
    scanf("%d",&t[i][j]);
}

void flipcol(int m)
{
    for(int i=0;i<N;i++)
      t[i][m]*=-1;
}
void fliprand(int n)
{
    for(int j=0;j<M;j++)
     t[n][j]*=-1;
}

int sumcol(int m)
{
   long s=0;
    for(int i=0;i<N;i++)
      s+=t[i][m];
    return s;
}

int sumrand(int n)
{
    long s=0;
    for(int j=0;j<M;j++)
     s+=t[n][j];
   return s;
}

int main()
{
_read();
int test=N*M; bool toif;
found.push_back(min);

 while(test)
 {
   toif=false;
   mini=min;
    for(int i=0;i<N;i++)
     for(int j=0;j<M;j++)
       if(t[i][j]<mini && find(found.begin(),found.end(),t[i][j])==found.end() ){ mini=t[i][j]; mink.y=j; mink.x=i; found.push_back(mini); toif=true;}

if(toif)
   if(sumrand(mink.x)<0 && sumcol(mink.y)<0)
   {
       if(sumrand(mink.x)<sumcol(mink.y))
          fliprand(mink.x);
        else flipcol(mink.y);

   } else
       {
       if(sumrand(mink.x)<0)
         fliprand(mink.x);
       if(sumcol(mink.y)<0)
         flipcol(mink.y);
        }
  test--;
 }

   for(int i=0;i<N;i++)
     for(int j=0;j<M;j++)
       REZ+=t[i][j];

 printf("%ld",REZ);
return 0;
}