#include <cstdio>
#include <iostream>
#include <vector>
#include <queue>
#include <utility>
#include <algorithm>
#include <functional>
#include <string>
#include <cstring>
#include <cmath>
#include <map>
#include <set>
#include <bitset>
#include <stack>
#include <iomanip>
#include <fstream>
#define MOD 9901
#define NMAX 505
#define INF 0x3f3f3f3f
#define pb push_back

using namespace std;

FILE *fin = freopen("culori.in", "r", stdin);
FILE *fout = freopen("culori.out", "w", stdout);

typedef pair<int, int> pii;

int v[NMAX], dp[NMAX][NMAX];

inline int memo(int st, int dr) {
	int &ret = dp[st][dr];

	if (ret != -1)
		return ret;
	if (st == dr)
		return ret = 1;
	if (v[st] != v[dr] || st > dr)
		return ret = 0;

	int i;
	ret = 0;
	for (i = st + 1; i < dr; ++i)
		ret = (ret + memo(st + 1, i)*memo(i + 1, dr)) % MOD;

	return ret;
}

int main() {
	int i, n, m, j;
	char ch;

	cin >> n;
	for (i = 1; i <= 2 * n - 1; ++i)
		cin >> v[i];

	memset(dp, -1, sizeof(dp));

	cout << memo(1, 2 * n - 1);

	return 0;
}