#include<fstream>
using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");
int main()
{
	int a[100][100],s = 0, n, m, i, j;
	fin >> n >> m;
	for ( i = 1; i <= n; i++ )
		for ( j = 1; j <= m; j++ )
			fin >> a[i][j];
		for ( i = 1; i <= n; i++ )
		{
			s = 0;
			for ( j = 1; j <= m; j++ )
				s += a[i][j];
			if ( s < 0 )
				for ( j = 1; j <= m; j++ )
					a[i][j] = a[i][j] *(-1);
		}
		for ( j = 1; j <= m; j++ )
		{
			s = 0;
			for ( i = 1; i <= n; i++ )
				s += a[i][j];
			if ( s < 0 )
				for ( i = 1; i <= n; i++ )
					a[i][j] =a[i][j]* (-1);
		}
		
	    s = 0;
		for ( i = 1; i <= n; i++ )
		for ( j = 1; j <= m; j++ )
			s+=a[i][j];
		fout << s;
		fin.close();
		fout.close();
		return 0;
}