#include <bits/stdc++.h>

#define NMAX 550
#define MOD 9901
using namespace std;

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

int dp[NMAX][NMAX], vec[NMAX];

int main()
{
    int n;
    fin >> n;

    n = 2 * n - 1;
    for(int i = 1; i <= n; ++i)
    {
        fin >> vec[i];
        dp[i][i] = 1;
    }

    for(int lg = 2; lg < n; lg += 2)
        for(int i = 1; i <= n - lg; ++i)
        {
            int j = i + lg;
            if(vec[i] == vec[j])
                for(int k = i; k <= j; ++k)
                    if(vec[i] == vec[k])
                        dp[i][j] = (dp[i][j] + (dp[i + 1][k - 1] * dp[k][j]) % MOD) % MOD;
        }
    fout << dp[1][n] << '\n';
    return 0;
}