var m,n,i,j,k:byte;a,s:longint;f,g:text;v:boolean;t:array[1..16,1..16] of longint;
begin
        assign(f,'flip.in');assign(g,'flip.out');reset(f);
        read(f,m);read(f,n);
        for i:=1 to m do
                for j:=1 to n do
                        read(f,t[i,j]);
        close(f);v:=true;
        while v=true do
        begin
                v:=false;
                for i:=1 to m do
                begin
                        s:=0;
                        for j:=1 to n do
                                s:=s+t[i,j];
                        if s<0 then
                        begin
                                v:=true;
                                for j:=1 to n do
                                        t[i,j]:=t[i,j]*-1;
                        end;
                end;
                v:=false;
                for i:=1 to n do
                begin
                        s:=0;
                        for j:=1 to m do
                                s:=s+t[j,i];
                        if s<0 then
                        begin
                                v:=true;
                                for k:=1 to m do
                                        t[k,i]:=t[k,i]*-1;
                        end;
                end;
        end;
        s:=0;
        for i:=1 to m do
                for j:=1 to n do
                        s:=s+t[i,j];
        rewrite(g);write(g,s);close(g);
end.