program culori;
var  f,g:text;
    i,n,j,k,p,d,s:integer;
    c:array[1..511] of 1..256;
    a:array[1..100,1..100] of integer;
begin
assign(f,'culori.in');
reset(f);
readln(f,n);
for i:=1 to 2*n-1 do
  read(f,c[i]);
close(f);
assign(g,'culori.out');
rewrite(g);
p:=2*n-1;
if c[1]<>c[p] then writeln(g,'0')
   else
    begin
      for i:=1 to p do a[i,i]:=1;
      for d:=2 to p do
         for i:=1 to p do
           for j:=d to p do
              begin
                if c[i]<>c[j] then a[i,j]:=0
                   else
                     begin
                       s:=0;
                       for k:=i+1 to j-1 do
                          if c[i+1]=c[k] then s:=s+a[i,k-1]+a[k+1,j];
                       a[i,j]:=s;
                     end;
              end;
        writeln(g,a[1,p]);

    end;
close(g);
end.