#include <bits/stdc++.h>
#define inf 1e9
using namespace std;
const int nmax = 512, mod = 9901;
int v[nmax + 1];
long long dp[nmax + 1][nmax + 1];
int main()
{
    ios :: sync_with_stdio(false);
    cin.tie(0);
    freopen("culori.in", "r", stdin);
    freopen("culori.out", "w", stdout);
    int n, i, j, d, k;
    cin >> n;
    n = n * 2 - 1;
    for(i = 1; i <= n; i++)
    {
        dp[i][i] = 1;
        cin >> v[i];
    }
    for(d = 2; d < n; d += 2)
    {
        for(i = 1; i + d <= n; i++)
        {
            j = i + d;
            if(v[i] != v[j])
                dp[i][j] = 0;
            else
            {
                dp[i][j] = dp[i + 1][j - 1];
                for(k = i + 1; k < j; k++)
                {
                    if(v[k] == v[i])
                    {
                        dp[i][j] += dp[i][k] * dp[k + 1][j - 1];
                        dp[i][j] %= mod;
                    }
                }
            }
        }
    }
    cout << dp[1][n];
    return 0;
}