using namespace std;
#include<cstdio>
#define MAX_N 256
#define Mod 9901
int A[512][512];
int C[512];
int N;
void read()
{
	freopen("culori.in","r",stdin);
	freopen("culori.out","w",stdout);
	scanf("%d",&N);
	int i;
	N = 2*N - 1;
	for(i=1;i <= N;++i)
		scanf("%d",&C[i]);
}
void dp()
{
	int start, i,j,k, x;
	for( start = 0; start <= N; start+=2)
	{
		for(x = 1; x+start<=N; ++x)		
		{
			i = x; j = start + x;
			if(i == j) { A[i][j] = 1; continue; }
			if(C[i]!=C[j]) { A[i][j] = 0; continue; }
			for(k = i+1; k<j; ++k)
				if(C[i+1] == C[k]) 
					{
					A[i][j] += A[i+1][k] * A[k+1][j];
					if(A[i][j] >= Mod) A[i][j] -= Mod;
					}
			
		}
	}	
	printf("%d\n",A[1][N]%Mod);
}
int main()
{
	read();
	dp();
	return 0;
}