#include<stdlib.h>
#include<cstdio>

using namespace std;

int main()
{int m,n,i,j,a[100][100],sd,ss,s;
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);
    
    scanf("%d%d",&m,&n);
    for (i=1;i<=m;i++)
        for (j=1;j<=n;j++)
        scanf("%d",&a[i][j]);
        
   
   for (i=1;i<=m;i++)
        {sd = 0; ss = 0;
        for (j=1;j<=n;j++)
        if (a[i][j] > 0) sd = sd + a[i][j];
                    else ss = ss + a[i][j];
        
        if (abs(ss) > sd)               
        for (j=1;j<=n;j++)
        a[i][j] = - a[i][j];
        }
        
   for (i=1;i<=n;i++)
        {sd = 0;ss = 0;
        for (j=1;j<=m;j++)
        if (a[j][i] > 0) sd = sd + a[j][i];
                    else ss = ss + a[j][i];
        
        if (abs(ss) > sd)
        for (j=1;j<=n;j++)
        a[j][i] = - a[j][i];
        }   
   
    
        s = 0;
    for (i=1;i<=m;i++)
        for (j=1;j<=n;j++)
        s = s + a[i][j];
        
        printf("%d",s);

return 0;
}