#include <iostream>
#include <stdio.h>
using namespace std;

int main()
{   FILE *f=fopen("flip.in","rt");
    FILE *g=fopen("flip.out","wt");
    int M,N,A[18][18],j,k;
    int i,s=0;
    fscanf(f,"%d %d",&N,&M);
    for (i=1;i<=N;i++)
        for (j=1;j<=M;j++)
                {fscanf(f,"%d",&A[i][j]);}
    for (i=1;i<=N;i++)
        { int sp=0,sn=0;
            for (j=1;j<=M;j++)
                if(A[i][j]>0)sp=sp+A[i][j];
                else sn=sn+(-1)*A[i][j];
            if(sn>sp)
                for (k=1;k<=M;k++) A[i][j]*=(-1);
        }
    for (j=1;j<=N;j++)
        { int sp=0,sn=0;
            for (i=1;i<=M;i++)
                if(A[i][j]>0)sp=sp+A[i][j];
                else sn=sn+(-1)*A[i][j];
            if(sn>sp)
                for (k=1;k<=M;k++) A[k][j]*=(-1);
        }
    for (i=1;i<=N;i++)
        for (j=1;j<=M;j++)s=s+A[i][j];
    fprintf(g,"%d",s);

    fclose(f);
    fclose(g);
    return 0;
}