using namespace std;
#include<cstdio>
#define MAX_N 258
#define Mod 9901
int A[2 * MAX_N+1][2 * MAX_N+1];
int C[2 * MAX_N + 1];
int N;
void read()
{
	freopen("culori.in","r",stdin);
	freopen("culori.out","w",stdout);
	scanf("%d",&N);
	int i;
	for(i=1;i < 2 * N;++i)
		{
		scanf("%d",&C[i]);
		A[i][i] = 1;
		}
}
void dp()
{
	int start, i,j,k;
	i = 1;
	j = 2;
	for( start = 2; start < 2*N; ++start)
	{
		i = 1; j = start;
		while( j < 2*N )
		{
			if( (i+j) % 2 == 0 && C[i] == C[j])
			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;
					}
			++i; ++j;
		}
	}	
	printf("%d\n",A[1][2*N-1]);
}
int main()
{
	read();
	dp();
	return 0;
}