var i,j,k,n,m,x,y,s,max:longint;
    a:array[0..200,0..200]of real;
    tot:real;
begin
assign(input,'long.in');reset(input);
assign(output,'long.out');rewrite(output);
readln(n,m);
for j:=1 to m do
  for i:=1 to n do
     read(a[i,j]);

max:=0;
for i:=1 to n do
 for j:=1 to m do
   begin
   tot:=0; s:=0;
   for x:=i to n do
    begin
      for y:=j to m do
        begin
        tot:=tot+a[x,y];
        s:=s+1;

        end;

     if (s>max)and(tot>0) then max:=s;
   end;
   end;
writeln(max);
end.