var sor:array[1..256] of byte;
{    a:array[1..25,1..25] of longint;}
    N,i,j:integer;
    t:text;

function summa(x,y:integer):longint;
          var k:integer;
              osz:longint;
          begin
          if (x+y) mod 2=1 then summa:=0 else
          if sor[x]<>sor[y] then summa:=0 else
          if x+1=y then summa:=0 else
          if x=y then summa:=1 else
          if x+2=y then summa:=1 else
          begin
          osz:=0;
           for k:=x+1 to y-1 do
            begin
             osz:=osz+(summa(x+1,k)*summa(k+1,y));
            end;
            summa:=osz;
            end;
          end;

begin
    assign(t,'culori.in');
    reset(T);
     read(t,N);
     n:=2*n-1;
     for i:=1 to n do read(t,sor[i]);

{     for i:=1 to n do for j:=1 to n do a[i,j]:=0;
     for i:=1 to n do a[i,i]:=1;}
    close(T);

{    for i:=1 to n do
     for j:=i+1 to n do
      if (i+j) mod 2=0 then
      if sor[i]=sor[j] then
      begin
       a[i,j]:=summa(i,j);
      end;}

     assign(t,'culori.out');
     rewrite(T);
     writeln(t,summa(1,n));
     close(T);

end.