var
 sum:array[0..30,0..100000] of longint;
 p:array[1..33] of longint;
 i,j,m,n,l,v,ml,k,limit,ct:longint;
 bbbb:boolean;
begin
 assign(input,'balline.in');reset(input);
 assign(output,'balline.out');rewrite(output);
 readln(n,k);
 p[1]:=1;
 randomize;
 for i:=2 to k do p[i]:=p[i-1]*2;
 for i:=1 to n do
  begin
   readln(m);
   for j:=1 to k do
    begin
    sum[j,i]:=sum[j,i-1];
    if m and p[j]=p[j] then inc(sum[j,i]);
    end;
  end;
 if n<=3000 then begin
 for i:=1 to n do
  begin
  for j:=1 to n-i+1 do
   begin
    v:=sum[1,j+i-1]-sum[1,j-1];
    bbbb:=true;
    for l:=2 to k do
      if sum[l,j+i-1]-sum[l,j-1]<>v then
       begin bbbb:=false;break; end;
    if bbbb then begin
     if i>ml then ml:=i;
    end;
   end;
  end;
 writeln(ml);
 end else begin
  ct:=0;
  repeat
    inc(ct);
    i:=random(n-ml)+1;
    j:=random(n-i+1)+1;
    v:=sum[1,j+i-1]-sum[1,j-1];
    bbbb:=true;
    for l:=2 to k do
      if sum[l,j+i-1]-sum[l,j-1]<>v then
       begin bbbb:=false;break; end;
    if bbbb then if  i>ml then ml:=i;
  until ct>1000000;
  writeln(ml);
  end;
 close(input);close(output);
end.