#include<fstream>
#include<string>
#include<iostream>
#include<vector>
#include<string.h>
using namespace std;
vector <string> splitText(string input)
{
	vector<string> output;
	string parcurgere="";
	cout << input.length();
	for (int i = 0; i < input.length(); i++)
	{
		cout << input.at(i) << endl;
		if (input.at(i) != ' ')
		{
			parcurgere += input[i];
		}
		else
		{
			output.push_back(parcurgere);
			parcurgere = "";
		}
	}
	return output;
}
int main()
{
	int n, m, out=0;
	int a;
	int matrice[20][20];
	string unu;
	vector <string> fields;
	ifstream f("flip.in");
	ofstream g("flip.out");
	f >> n;
	f >> m;
	for (int i = 0; i < n; i++)
	{
		for (int j = 0; j < m; j++)
		{
			f >> a;
			if (a < 0)
			{
				out += (-1)*a;
			}
			else
			{
				out += a;
			}
		}
	}

	g << out;
	f.close();
	g.close();
	system("pause");
	return 0;

}