#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';
	return 0;
}