program bing;
const
 go:array[1..3,1..2] of integer=((1,-1),(1,0),(1,1));
var
 f1,f2:text;
 w,l,i:integer;
 max,s:longint;
 a:array[1..100,1..10] of longint;
procedure init;
var
 i,j:integer;
begin
 assign(f1,'azshara.in');reset(f1);
 assign(f2,'azshara.out');rewrite(f2);
 readln(f1,w,l);
 for i:=1 to l do
 for j:=1 to w do
 read(f1,a[i,j]);
 max:=0;
end;
procedure nb(x,y:integer);
var
 i,j:integer;
begin
 s:=s+a[x,y];
 for i:=1 to 3 do
  begin
   if (y+go[i,2]>=1)and(y+go[i,2]<=w) then
   begin
    if x+go[i,1]>l then
                    begin
                     if s>max then max:=s;
                    end

    else
    begin
     if a[x+go[i,1],y+go[i,2]]>-1 then
     nb(x+go[i,1],y+go[i,2]);
    end;
   end;
  end;
 s:=s-a[x,y];
end;
begin
 init;
 for i:=1 to w do
  begin
  s:=0;
  nb(1,i);
  end;
 write(F2,max);
 close(f1);
 close(f2);
end.