const maxn=520;modu=9901;oo=maxlongint div 4;
var t:Text;
    A,X:Array[0..maxn]of longint;
    V:array[0..maxn,0..maxn]of longint;
    i,n,j,lung,lg,k:longint;
{    var t1:longint;t2:longint absolute $0:$046c;}
begin
 {  t1:=t2;}
   assign(t,'culori.in');reset(T);readln(T,n);n:=n*2-1;
   for i:=1 to N do read(t,A[i]);close(T);for i:=1 to N do V[i,i]:=1;
   for lung:=1 to N-1 do
   for i:=1 to N-lung do
   if A[i]=A[i+lung] then
   begin
      j:=i+lung;lg:=0;
      for k:=i to j do if A[i]=A[k] then begin inc(lg);X[lg]:=k;end;
      V[i,j]:=V[i+1,j-1];
      for k:=1 to lg-1 do
      begin
         V[i,j]:=V[i,j]+V[i,X[k+1]]*V[X[k+1]+1,X[lg]-1];
         if V[i,j]>oo then V[i,j]:=V[i,j]mod modu;
      end;
      v[i,j]:=v[i,j] mod modu;
   end;
   assign(T,'culori.out');rewrite(t);writeln(t,V[1,n]);close(T);
{   writeln((t2-t1)/18.2:0:6);}
end.