#include <fstream>
#define DIMN 600
#define modulo 9901

using namespace std;

ifstream f("culori.in");
ofstream g("culori.out");

int n;

int v[DIMN], D[DIMN][DIMN];

int main() {
    f >> n;
    n = 2*n - 1;
    for (int i=1; i<=n; ++i) {
        D[i][i] = 1;
        f >> v[i];
    }
    for (int i=2; i<=n; i+=2) {
        for (int j=1; j+i<=n; ++j) {
            if (v[j] != v[i+j])
                continue;
            for (int k=j+1; k<=j+i; ++k) {
                D[j][i+j] += D[j+1][k-1]*D[k][i+j]%modulo;
                D[j][i+j] %= modulo;
            }
        }
    }
    g << D[1][n]%modulo << "\n";
    return 0;
}