#include <iostream.h>
#include <fstream.h>

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

int M,N,a[50][50];

void flip (int l, int c);
int suma ();

int main ()
{

int i,j,s,max;

in>>N>>M;

for (i=0;i<N;i++)
 for (j=0;j<M;j++)
  in>>a[i][j];

flip (1,1);
max=suma();
flip (1,1);

for (i=0;i<N;i++)
 for (j=0;j<M;j++)
 {
 flip (i+1,j+1);
 s=suma();
 if (max<s)
  max=s;
 flip (i+1,j+1);
 }

out<<max;

return 0;
}


void flip (int l, int c)
{
int i;
l--;
c--;
for (i=0;i<M;i++)
 a[l][i]*=-1;    
for (i=0;i<N;i++)
 a[i][c]*=-1;    
}

int suma ()
{
int i, j,s=0;
for (i=0;i<N;i++)
 for (j=0;j<M;j++)
  s+=a[i][j];

return s;
}