var n,i,sum,max,aux,j,m,k,min:longint;
    a,b:array[1..50,1..50]of longint;
    phi:array[1..100]of longint;
    f1,f2:text;
begin
assign(f1,'flip.in'); reset(f1);
assign(f2,'flip.out'); rewrite(f2);
read(f1,n);
read(f1,m);
for i:=1 to n do
    for j:=1 to m do
        read(f1,a[i,j]);
for i:=1 to n do
    for j:=1 to m do
        b[i,j]:=a[i,j];
for i:=1 to n do
    for j:=1 to m do
        if b[i,j]>0 then phi[j]:=phi[j]+b[i,j];
min:=1000001;
for i:=1 to m do
    if min>phi[i] then
       begin
            min:=phi[i];
            aux:=i;
       end;
for i:=1 to m do
    phi[i]:=0;
for i:=1 to n do
    a[i,aux]:=a[i,aux]*-1;
for i:=1 to n do
    for j:=1 to m do
        if b[i,j]>0 then phi[i]:=phi[i]+b[i,j];
min:=1000001;
for i:=1 to n do
    if min>phi[i] then
       begin
            min:=phi[i];
            aux:=i;
       end;
for j:=1 to m do
    a[aux,j]:=a[aux,j]*-1;
for i:=1 to n do
    for j:=1 to m do
        sum:=sum+a[i,j];
write(f2,sum);
close(f1);
close(f2);
end.