#include<stdio.h>
int main()
{
    int n,m,i,j,ok=1;
    long int a[16][16],s;
    FILE *f=fopen("flip.in","r"),*g=fopen("flip.out","w");
    fscanf(f,"%d %d",&n,&m);
    for(i=0;i<n;i++)
            for(j=0;j<m;j++)
                fscanf(f,"%ld",&a[i][j]);
while(ok){
    ok=0;
     for(i=0;i<n;i++){
         s=0;
            for(j=0;j<m;j++)
              s+=a[i][j];
            if(s<0) {for(j=0;j<m;j++)
                        a[i][j]=-a[i][j];
                        ok=1;
                    }
     }
     for(j=0;j<m;j++){
         s=0;
            for(i=0;i<n;i++)
                s+=a[i][j];
            if(s<=0) {for(i=0;i<n;i++)
                        a[i][j]=-a[i][j];
                        ok=1;
                    }
     }
}
     s=0;
     for(i=0;i<n;i++)
            for(j=0;j<m;j++)
                s+=a[i][j];
     fprintf(g,"%ld",s);
     return 0;
}