#include<stdio.h>
int main () {
	int n,m,v[100][100],i,j,x=1,s=0;
	FILE *in=fopen("flip.in","r"), *out=fopen("flip.out","w");
	fscanf(in,"%d%d",&n,&m);
	for(i=0;i<n;i++)
		for(j=0;j<m;j++)
			fscanf(in,"%d",&v[i][j]);
	while(x){
		x=0;
		for(i=0;i<n;i++){
			for(j=0;j<m;j++)
				s+=v[i][j];
			if(s<0){
				x=1;
				for(j=0;j<m;j++)
					v[i][j]*=-1;
			}
			s=0;
		}
		for(i=0;i<m;i++){
			for(j=0;j<n;j++)
				s+=v[j][i];
			if(s<0){
				x=1;
				for(j=0;j<n;j++)
					v[j][i]*=-1;
			}
			s=0;
		}
	}
	for(i=0;i<n;i++)
		for(j=0;j<m;j++)
			s+=v[i][j];
	fprintf(out,"%d",s);
	fclose(in);
	fclose(out);
	return 0;
}