#include <fstream>

#define MOD 9901
#define DIM 700

using namespace std;

ifstream fin("culori.in");
ofstream fout("culori.out");

int N, D[DIM][DIM], v[DIM];

int main()
{
    fin >> N;

    N = 2 * N - 1;

    for(int i = 1; i <= N; i ++)
    {
        fin >> v[i];
        D[i][i] = 1;
    }

    for(int L = 3; L <= N ; L += 2)
    {
        for(int i = 1; i + L - 1 <= N; i ++)
        {
            int j = i + L - 1;

            if(v[i] != v[j])
            {
                continue;
            }

            for(int k = i + 1; k < j; k ++)
            {
                D[i][j] = (D[i][j] + D[i + 1][k] * D[k + 1][j]) % MOD;
            }


        }
    }

    fout << D[1][N];


    return 0;
}