#include<cstdio>
using namespace std;
int n,E[280],D[280][280];
int main()
{
    int i,j,k,l;
    freopen("culori.in","r",stdin);
    freopen("culori.out","w",stdout);
    scanf("%d",&n);
    for (i=1;i<2*n;++i)
        scanf("%d",&E[i]), D[i][i]=1;
    for (l=2;l<2*n;++l)
        for (i=1;i+l<2*n;++i)
        {
            j=i+l;
            if (E[i]==E[j])
                for (k=i+2;k<=j;++k)
                    if (E[i]==E[k])
                        D[i][j]+=D[i+1][k-1]*D[k][j], D[i][j]%=9901;
        }
    printf("%d\n",D[1][2*n-1]);
    return 0;
}