Pascal :

program balance;
var c,s:array[0..100000,0..50] of longint;
    pos:array[0..100000] of longint;
    t:array[0..100000] of string;
    n,tc,j,k,i,a,start,ans:longint;
    now:string;
    can:boolean;
procedure change(k:longint);
var now,tip:longint;
begin
now:=k;
tip:=0;
while now<>0 do begin
 inc(tip);
 c[i,tip]:=now mod 2;
 now:=now div 2;
 end;
end;

procedure qsort(a,b:longint);
var i,j,temp1,y:longint;
    x,temp:string;
begin
i:=a;
j:=b;
x:=t[(a+b) div 2];
y:=pos[(a+b) div 2];
repeat
 while (t[i]<x) or ((t[i]=x) and (pos[i]<y)) do inc(i);
 while (t[j]>x) or ((t[j]=x) and (pos[j]>y)) do dec(j);
 if i<=j then begin
  temp:=t[i];
  t[i]:=t[j];
  t[j]:=temp;
  temp1:=pos[i];
  pos[i]:=pos[j];
  pos[j]:=temp1;
  inc(i);
  dec(j);
 end;
until i>j;
if i<b then qsort(i,b);
if a<j then qsort(a,j);
end;

procedure deal(w:longint);
var i,kk:longint;
ch:string;
begin
for i:=1 to k do
 s[w,i]:=s[w-1,i]+c[w,i];
for i:=1 to k-1 do
  begin
   kk:=s[w,i+1]-s[w,i];
   str(kk,ch);
   t[w]:=t[w]+ch;
  end;
pos[w]:=w;
end;

begin
//assign(input,'balance.in');
//assign(output,'balance.out');
//reset(input);
//rewrite(output);
readln(n,k);
for i:=1 to n do
 begin
  readln(a);
  change(a);
   deal(i);
 end;
for i:=1 to k-1 do
 t[0]:=t[0]+'0';
qsort(0,n);
for i:=1 to n do
 begin
  can:=true;
  tc:=c[i,1];
  for j:=2 to k do
   if c[i,j]<>tc then begin can:=false; break; end;
  if can then begin ans:=1;  break; end;
 end;
now:=t[0];
start:=pos[0];
for i:=1 to n do
 begin
  if t[i]<>now then
   begin
    if pos[i-1]-start>ans then ans:=pos[i-1]-start;
    start:=pos[i];
    now:=t[i];
   end;
 end;
if pos[i]-start>ans then ans:=i-start;
writeln(ans);
//close(input);
//close(output);
end.