#include <fstream>
#define DIM 600
#define MOD 9901

using namespace std;

long long c[DIM];
long long a[DIM][DIM];
long long i,j,k,n,d;

int main(){
    ifstream fin ("culori.in");
    ofstream fout("culori.out");
    fin>>n;
    n=2*n-1;
    for (i = 1;i<=n;i++) {
        fin>>c[i];
        a[i][i] = 1;
    }

    for (d = 2; d<=n; d++){
        for (i=1;i+d-1<=n;i++) {
            j = i+d-1;
            if (d%2 == 0 || c[i]!=c[j])
                a[i][j] = 0;
            else {
                for (k=i+1;k<j;k++)
                    a[i][j]+=(a[i+1][k]*a[k+1][j]);
                a[i][j]%=MOD;
            }
        }
    }

    fout<< a[1][n];
    return 0;
}