var a:array[1..300,1..300] of longint;

b:array[1..300] of longint;

sum,max:int64;

i,j,k,l,m,n,h:longint;

begin

readln(n,m);

for i:=1 to n do begin

for j:=1 to m do

begin

read(a);

if a=0 then a:=-maxlongint;

end;

readln;

end;

for i:=1 to n do

begin

fillchar(b,sizeof(b),0);

for j:=i to n do

begin

for k:=1 to m do

b[k]:=b[k]+a[j,k];

sum:=0;

for l:=1 to m do

begin

sum:=sum+b[l];

if sum>max then max:=sum;

if sum