#include <stdio.h>
#include <stdlib.h>

int main()
{
    FILE* fr = fopen ("flip.in", "r");
    FILE* fw = fopen ("flip.out", "w");
    if( !fr )
        return -1;
    int N, M, a[16][16];
    fscanf(fr,"%d%d", &N,&M);
    for( int i = 0; i < N ; i++)
        for(int j = 0; j < M; j++)
            fscanf(fr,"%d", &a[i][j]);
    int s = 0;
    for( int i = 0; i < N ; i++)
    {
        s = 0;
        for(int j = 0; j < M; j++)
            s += a[i][j];
        if(s < 0)
            for(int j = 0; j < M; j++)
                a[i][j] = -a[i][j];

    }
    for( int j = 0; j < M ; j++)
    {
        s = 0;
        for(int i = 0; i < N; i++)
            s += a[i][j];
        if(s < 0)
            for(int i = 0; i < N; i++)
                a[i][j] = -a[i][j];

    }
    int sf = 0;
    for( int i = 0; i < N ; i++)
        for(int j = 0; j < M; j++)
            sf += a[i][j];

    fprintf(fw,"%d ",sf );



    return 0;
}