const maxn=200000 ;
var n,k,i,j,num,z,p,sum,ans:longint;
    height,rank,sa,y,x,a:array[0..maxn]of longint;

procedure sort(l,r:longint);
var i,j,k,p,t:longint;
begin
  i:=l;j:=r;k:=x[(i+j)>>1];p:=y[(i+j)>>1];
  repeat
    while (x[i]<k)or((x[i]=k)and(y[i]<p)) do inc(i);
    while (x[j]>k)or((x[j]=k)and(y[j]>p)) do dec(j);
    if i<=j then
      begin
        t:=x[i];x[i]:=x[j];x[j]:=t;
        t:=y[i];y[i]:=y[j];y[j]:=t;
        t:=sa[i];sa[i]:=sa[j];sa[j]:=t;
        inc(i);dec(j);
      end;
  until i>j;
  if i<r then sort(i,r);
  if j>l then sort(l,j);
end;
procedure make_height;
begin
z:=0;
//for i:=1 to n do write(a[i],' ');
for i:=1 to n do
    begin
      if rank[i]=1 then continue;
      if z<=0 then z:=0 else dec(z);
      while a[i+z]=a[sa[rank[i]-1]+z] do inc(z);
      height[rank[i]]:=z;

    end;

end;
procedure init;
begin
  readln(n,k);
  fillchar(a,sizeof(a),255);
  p:=0;
  for i:=1 to n do
    begin
       readln(a[i]);

       rank[i]:=a[i];
       if a[i]>p then p:=a[i];
    end;
  if p=0 then
    begin
      writeln(n);
      halt;
    end;
  p:=1;

  while p<=n-1 do
    begin
      for i:=1 to n do sa[i]:=i;
      for i:=1 to n do x[i]:=rank[i];
      for i:=1 to n do y[i]:=rank[i+p];
      sort(1,n);
      sum:=1;
      rank[sa[1]]:=1;
      for i:=2 to n do
        begin
          if (x[i]<>x[i-1])or(y[i]<>y[i-1]) then inc(sum);
          rank[sa[i]]:=sum;
        end;
      if sum=n then break;
      p:=p * 2;
    end;

  make_height;


end;
function max(x,y:longint):longint;
begin
  if x<y then exit(y);
  exit(x);
end;
procedure main;
begin
  num:=1;
  ans:=0;
  for i:=2 to n do
    begin
      if height[i]>height[i-1] then
        begin
          inc(num);
          if num>=k then ans:=max(ans,height[i-k+2]);
        end
                               else num:=1;

    end;
  writeln(ans);
end;
begin
  init;
  main;
end.