program xxxx;
var w,n,m,i,i1,j,j1:longint;
    a:array[1..200,1..200] of real;

function pd(x1,x2,x3,x4:longint):boolean;
var p,q:longint;
    x:real;
begin
  x:=0;
  for p:=x1 to x3 do
    for q:=x2 to x4 do
      x:=x+a[p,q];
  if x>0 then
    pd:=true
  else
    pd:=false;
end;

function max(x,y:longint):longint;
begin
  if x>y then
    max:=x
  else
    max:=y;
end;


begin
  assign(input,'long.in');
  reset(input);
  assign(output,'long.out');
  rewrite(output);
  read(n,m);
  w:=0;
  for i:=1 to n do
    for j:=1 to m do
      read(a[i,j]);
  for i:=1 to n do
    for i1:=1 to m do
      for j:=i to n do
        for j1:=i1 to m do
          begin
            if pd(i,i1,j,j1) then
              w:=max(w,(j-i+1)*(j1-i1+1));
          end;
  write(w);
  close(input);
  close(output);
end.