#include <fstream>
using namespace std;
int main()
{int k,n,m,i,j,s,min,a;
ifstream f("flip.in");
ofstream g("flip.out");
int v[16][16],b[16];
f>>n;
f>>m;
i=0;
s=0;
a=0;
while(i<=n)
{i++;
    j=1;
    min=100000000000000000000;
    while(j<m)
    {f>>v[i][j];
    k=v[i][j];
    if(k<0)
    k=k*(-1);
    if(min>k)
    min=k;
    s=s+k;
j++;}
s=s-min;}
g<<s;
return 0;
}