记录编号	39468	评测结果	AAAAAAAAAAAA
题目名称	平衡奶牛	最终得分	100
用户昵称	wo shi 刘畅	是否通过	通过
代码语言	Pascal	运行时间	0.613 s
提交时间	2012-07-11 19:18:01	内存使用	69.59 MiB

const
  hash=17173;
  base=1717173;

var
  i,j,x,n,total,k,ans:longint;
  now:int64;
  s,b:array[0..100000,0..30]of longint;
  first:array[-2000000..2000000]of longint;
  point,next:array[0..4000000]of longint;

function ok(l,r:longint):boolean;
var
  i:longint;
begin
  for i:=2 to k do
  if b[l,i]<>b[r,i] then exit(false);
  exit(true);
end;

procedure insert(now,r:longint);
var
  i,j:longint;
begin
  i:=first[now];
  while i<>-maxlongint do
  begin
    j:=point[i];
    if ok(j,r) then
    begin
      if r-j>ans then ans:=r-j;
      exit;
    end;
    i:=next[i];
  end;
  inc(total);
  point[total]:=r;
  next[total]:=first[now];
  first[now]:=total;
end;

begin
  assign(input,'balline.in'); reset(input);
  assign(output,'balline.out'); rewrite(output);
  readln(n,k);
  for i:=1 to n do
  begin
    read(x);
    for j:=1 to k do
    s[i,j]:=s[i-1,j]+((x >> (j-1)) and 1);
  end;

  for i:=1 to n do
   for j:=2 to k do
   b[i,j]:=s[i,j]-s[i,j-1];
  for i:=-1717173 to 1717173 do
  begin
    first[i]:=-maxlongint;
    point[i]:=-maxlongint;
  end;
  for i:=0 to n do
  begin
    now:=0;
    for j:=2 to k do
    now:=(now*hash+b[i,j]) mod base;
    insert(now,i);
  end;
  writeln(ans);
  close(input);
  close(output);
end.