#include<cstdio>
#include<cstring>
int m,n,smax,v[18],x[18][18],y[18][18],k,j,i,s,sl;
FILE *f,*g;
int main(){
    f=fopen("flip.in","r");
    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",&x[i][j]);
            smax+=x[i][j];
        }
    }
    memcpy(y,x,sizeof(x));
    smax=0;
    while(v[0]==0){
        i=m;
        while(v[i]==1){
            v[i]=0;
            i--;
        }
        v[i]++;
        s=0;
        for(i=1;i<=m;i++){
            if(v[i]==1){
                for(j=1;j<=n;j++){
                    x[j][i]*=-1;
                }
            }
        }
        for(i=1;i<=n;i++){
            sl=0;
            for(j=1;j<=m;j++){
                sl+=x[i][j];
            }
            if(sl<0){
                for(j=1;j<=m;j++){
                    x[i][j]*=-1;
                }
            }
        }
        for(i=1;i<=n;i++){
            for(j=1;j<=m;j++){
                s+=x[i][j];
            }
        }
        if(s>smax)
            smax=s;
        memcpy(x,y,sizeof(y));
    }
    fprintf(g,"%d",smax);
    fclose(f);
    fclose(g);
return 0;
}