#include <fstream>
using namespace std;

ifstream input("culori.in");
ofstream output("culori.out");
int val[1000];
int vect[1000][1000];
int n,i,j,k;

int main() {
    input >> n;
    n = 2*n-1;
    for (i=1;i<=n;i++) {
        input >> val[i];
        vect[i][i] = 1;
    }
    for (j=1;j<=n;j++) {
        for (i=1;i<=n;i++) {
            if (val[i] == val[i+j]) for (k=i+1;k<i+j;k++) {
                vect[i][i+j] = (vect[i][i+j] + vect[i+1][k] * vect[k+1][i+j])%9901;
            }
        }
    }
    output << vect[1][n];
    return 0;
}