#include <fstream>
using namespace std;

ifstream F("culori.in");
ofstream G("culori.out");

const int Nmax=270;
const int Mmax=4*Nmax;
const int Mod=9901;

int N,M;
int D[Mmax][Mmax],A[Mmax];

int main()
{
	F>>N; 
	M=2*N-1;
	
	for (int i=1;i<=M;++i)
		F>>A[i],
		D[i][i]=1;
	
	for (int l=1;l<=M;++l)
		for (int i=1;i<=M;++i)
			if( A[i]==A[i+l] )
				for(int k=i+1; k<i+l; ++k)
					D[i][i+l]=(D[i][i+l]+D[i+1][k]*D[k+1][i+l])%Mod;
	
	G<<D[1][M]<<'\n';
}