#include<fstream.h>

long x[100][100],n,m,i,j,aux,a,b,c;

  int main ()

	{
	   ifstream fin("flip.in");

	   ofstream fout("flip.out");

	   fin>>n>>m;

	   for ( i=1 ; i<=n ; i++ )

		   for ( j=1; j<=m; j++ )

			   fin>>x[i][j];

	   for ( i=1; i<=n; i++ )

		   {  a=0;

			  for( j=1; j<=m; j++ )

				 a+=x[i][j];

			  if(a<0) for( j=1; j<=m; j++ )

						x[i][j]*=-1;

		   }

	   for ( i=1; i<=m; i++ )

		   {  a=0;

			  for( j=1; j<=n; j++ )

				 a+=x[j][i];

			  if(a<0) for( j=1; j<=n; j++ )

						x[j][i]*=-1;

		   }

	   for ( i=1; i<=n; i++ )

		   for ( j=1; j<=m; j++ )

			   b+=x[i][j];

	   fout<<b;

	   fin.close();

	   fout.close();

	   return 0;

	}