#include<stdio.h>
int N,M,i,j,v[16][16],s,sp;
using namespace std;

int main()
{FILE*f=fopen("flip.in","r");
FILE*g=fopen("flip.out","w");
fscanf(f,"%d %d ",&N,&M);
   for(i=1;i<=N;i++){
    for(j=1;j<=M;j++){
    fscanf(f,"%d",&v[i][j]);
    }
   }

   for(i=1;i<=N;i++){
       sp=0;
    for(j=1;j<=M;j++){
      sp=sp+v[i][j];

    }if(sp<0){
    for(j=1;j<=M;j++){v[i][j]=-v[i][j];
    }
    }
    }
   for(j=1;j<=M;j++){
       sp=0;
     for(i=1;i<=N;i++){
      sp=sp+v[i][j];}

    if(sp<0){
    for(i=1;i<=N;i++){v[i][j]=-v[i][j];
    }
    }
   }
   for(i=1;i<=N;i++){
    for(j=1;j<=M;j++){
        s=s+v[i][j];}}
        fprintf(g,"%d",s);
   fclose(f);
   fclose(g);
    return 0;
}