#include <fstream>
#define MOD 9901
using namespace std;
const int nmax=1e3+3;
int n,k,v[nmax],d[nmax][nmax],i,j,l;
ifstream f ("culori.in");
ofstream g ("culori.out");
int main ()
{
    f>>n;
    for(i=1;i<=2*n-1;++i) f>>v[i];
    n=2*n-1;
    for(i=1;i<=n;++i) d[i][i]=1;
    for(l=1;l<=n;++l)
    {
        for(i=1;i<=n-l+1;++i)
        {
            j=i+l-1;
            if(v[i]==v[j])
            for(k=i+1;k<j;++k) if(v[i+1]==v[k]) d[i][j]=(d[i][j]+(d[i+1][k]*d[k+1][j]))%MOD;
        }
    }
    g<<d[1][n];
    return 0;
}