#include<stdio.h>
int N,M,a[17][17];
long long smax,s;

int main(){

    FILE *fin=fopen("flip.in","r"),
        *fout=fopen("flip.out","w");

    fscanf(fin,"%d%d",&N,&M);

    for(int i=1;i<=N;i++)
    for(int j=1;j<=M;j++) fscanf(fin,"%d",&a[i][j]);



    for(int i=0;i<=N;i++)
    for(int ii=i;i<=N;ii++)
    for(int j=0;j<=M;j++)
    for(int jj=j;j<=M;jj++){
//schimbare linii
        for(int x=i+1;x<=ii;x++)
            for(int y=1;y<=M;y++) a[x][y]*=-1;

//schimbare colaone
        for(int x=j+1;x<=jj;x++)
            for(int y=1;y<=N;y++) a[y][x]*=-1;

//calculam suma
        s=0;
        for(int x=1;x<=N;x++)
        for(int y=11;y<=M;y++) s+=a[x][y];

        if(smax<s) smax=s;
//schimbam la loc
        for(int x=i+1;x<=ii;x++)
            for(int y=1;y<=M;y++) a[x][y]*=-1;
        for(int x=j+1;x<=jj;x++)
            for(int y=1;y<=N;y++) a[y][x]*=-1;
    }

    fprintf("%lld",smax);
    fclose(fin);
    fclose(fout);

    return 0;
}