#include <bits/stdc++.h>

using namespace std;

int N, M, A[20][20], i, j, s;

int main()
{
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);

    scanf("%d%d",&N,&M);

    for(i=1 ; i<=N ; ++i)
        for(j=1 ; j<=M ; ++j)
            scanf("%d",&A[i][j]),A[i][0]+=A[i][j],A[0][j]+=A[i][j];


    for(j=1 ; j<=M ; ++j)
        if(A[0][j]<0){

            A[0][j]*=-1;
            for(i=1 ; i<=N ; ++i)
                A[i][j]*=-1;
        }

    for(i=1 ; i<=N ; ++i)
        if(A[i][0]<0){

            A[i][0]*=-1;
            for(j=1 ; j<=M ; ++j)
                A[i][j]*=-1;

        }


    for(i=1 ; i<=N ; ++i)
        for(j=1; j<=M ; ++j)
                s+=A[i][j];



    printf("%d",s);

    return 0;
}