#include<stdio.h>
int n,m,a[101][101];
void Rezolvare(){
    int i,j,s,ss,k,l,min=-1,poz,ind;
    scanf("%d%d",&n,&m);
    for(i=1; i<=n; ++i)
        for(j=1; j<=m; ++j)
            scanf("%d",&a[i][j]);
    while(min<0){
        min=16000001;
        for(i=1, k=1; i<=n, k<=m; ++i, ++k){
            s=0;
            ss=0;
            for(j=1, l=1; j<=m, l<=n; ++j, ++l){
                s+=a[i][j];
                ss+=a[l][k];}
            if(s<min){
                poz=i;
                min=s;
                ind=1;}
            if(ss<min){
                poz=k;
                min=ss;
                ind=2;}}
        if(ind==1&&min<0)
            for(i=1; i<=m; ++i)
                a[poz][i]*=-1;
        else if(ind==2&&min<0)
            for(i=1; i<=n; ++i)
                a[i][poz]*=-1;}
    s=0;
    for(i=1; i<=n; ++i)
        for(j=1; j<=m; ++j)
            s+=a[i][j];
    printf("%d",s);}
int main(){
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);
    Rezolvare();
    return 0;}