#include<cstdio>
using namespace std;
int n,E[520],D[520][520];
int main()
{
    int i,j,k,l;
    freopen("culori.in","r",stdin);
    freopen("culori.out","w",stdout);
    scanf("%d",&n);
    n<<=1, --n;
    for (i=1;i<=n;++i)
        scanf("%d",&E[i]), D[i][i]=1;
    for (l=2;l<n;++l)
        for (i=1;i+l<=n;++i)
            if (E[i]==E[i+l])
            {
                j=i+l;
                for (k=i+2;k<=j;++k)
                    D[i][j]+=D[i+1][k-1]*D[k][j], D[i][j]%=9901;
            }
    printf("%d\n",D[1][n]);
    return 0;
}