const maxn = 256;
      modul = 9901;
      maxm = 2*maxn;

var f:text;
    n,m,i,j,k:longint;
    a:array[1..maxm]of longint;
    c:array[1..maxm,1..maxm]of longint;

procedure readdata;
begin
   assign(f,'culori.in');
   reset(f);
   readln(f,n);
   m:=2*n-1;
   for i:=1 to m do
   begin
      read(f,a[i]);
      c[i,i]:=1;
   end;
   close(f);
end;

procedure solve;
begin
   for i:=m-1 downto 1 do
   begin
      for j:=i+1 to m do
      begin
         if (i<>j) and (a[i]=a[j]) and ((i+j) mod 2=0) then
         begin
            for k:=i+1 to j-1 do
            begin
               c[i,j]:=(c[i,j]+((c[i+1,k]*c[k+1,j]) mod modul)) mod modul;
            end;
         end;
      end;
   end;
end;

procedure writedata;
begin
   assign(f,'culori.out');
   rewrite(f);
   writeln(f,c[1,m]);
   close(f);
end;

begin
   readdata;
   solve;
   writedata;
end.