#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
#include <cmath>

using namespace std;

#define mp make_pair
#define pb push_back
#define ll long long

#define maxN (2 * 277)
#define mod 9901

int n, i, j;
int v[maxN];
int dp[maxN][maxN];

int solve(int l, int r) {
    int i;

    if (dp[l][r] == -1) {
        if (l == r) return dp[l][r] = 1;
        if (l > r) return dp[l][r] = 0;
        dp[l][r] = 0;

        if (v[l] != v[r]) return 0;

        for (i = l + 1; i <= r; i++)
            if (v[i] == v[l])
                dp[l][r] += (solve(l + 1, i - 1) * solve(i, r)) % mod;

        dp[l][r] %= mod;
    }

    return dp[l][r];
}

int main()
{
    freopen("culori.in","r",stdin);
    freopen("culori.out","w",stdout);

    scanf("%d", &n); n = 2 * n - 1;
    for (i = 1; i <= n; i++) {
        scanf("%d", &v[i]);
        for (j = 1; j <= n; j++)
            dp[i][j] = -1;
    }

    printf("%d", solve(1, n));


    return 0;
}