Program flip;
var n,m,i,j,sum,total,k:integer;
    num:array[1..16,1..16] of integer;
    f1,f2:textfile;
begin
assign(f1,'flip.in');
assign(f2,'flip.out');
reset(f1);
rewrite(f2);
readln(f1,n,m);
for i:=1 to n do 
begin
for j:=1 to m do
read(f1,num[i][j]);
end;

for i:=1 to n do
begin
for j:=1 to m do
begin
sum:=sum+num[i][j];


end;

if sum<0 then
begin
for k:=1 to m do
begin
num[i][k]:=num[i][k]*(-1);
end;
end;
sum:=0;
end;


for i:=1 to m do
begin
for j:=1 to n do
begin
sum:=sum+num[j][i];


end;

if sum<0 then
for k:=1 to n do
num[k][i]:=num[k][i]*(-1);
sum:=0;
end;



for i:=1 to n do
begin
for j:=1 to m do 
total:=total+num[i,j]

end;
writeln(f2,total);
close(f1);
close(f2);

end.