#include <iostream>
#include<fstream>
#include<algorithm>
using namespace std;
ifstream in("flip.in");
ofstream out("flip.out");
int main()
{
    long n,i,j,s=0,d=0,v[17][17],m;
    in>>n;
    in>>m
    for(i=1;i<=n;i++)
    {

        for(j=1;j<=m;j++)
        {
            in>>v[i][j];
               if(v[i][j]>0)
                  s=s+v[i][j];
               else
                 d=d+v[i][j];
        }
    }
    if(s-d>d-s)
      out<<s-d;
    else
      out<<d-s;


   return 0;
}