#include<iostream>

#include<fstream>

using namespace std;

int main(){
	int v[19][19];
	int M,N,i,j;
	ifstream in("flip.in");
	ofstream OUT("flip.out");
	in>>N>>M;
	for(i=0;i<N;i++)
	for(j=0;j<M;j++){
			cin>>v[i][j];
	}
	int suma2=0,suma=0;
	for(i=0;i<N;i++){
	
	for(j=0;j<M;j++){
		suma+=v[i][j];
	}
	if(suma<0){
		suma=-suma;
}
	suma2+=suma;	
}
	out<<suma2;
	return 0;
}