#include<stdio.h>
FILE *f=fopen("flip.in","r"),*g=fopen("flip.out","w");
int a[17][17],n,m;
void citire()
{int i,j;
fscanf(f,"%d",&n);
fscanf(f,"%d",&m);
for(i=0;i<n;i++)
	{for(j=0;j<m;j++)
		{fscanf(f,"%d",&a[i][j]);
		}
	}
}
void make()
{int i,j;long sum;
for(i=0;i<m;i++)
	{sum=0;
	for(j=0;j<n;j++)
		{sum=sum+a[j][i];
		}
	if(sum<0)
		{for(j=0;j<n;j++)
			{a[j][i]=a[j][i]*(-1);
			}
		}
	}
for(i=0;i<n;i++)
	{sum=0;
	for(j=0;j<m;j++)
		{sum=sum+a[i][j];
		}
	if(sum<0)
		{for(j=0;j<m;j++)
			{a[i][j]=a[i][j]*(-1);
			}
		}
	}
}
int main()
{long sum;
int i,j;
citire();
make();
sum=0;
for(i=0;i<n;i++)
	{for(j=0;j<m;j++)
		{sum=sum+a[i][j];
		}
	}
fprintf(g,"%ld",sum);
fclose(f);
fclose(g);
return 0;
}