#include <fstream>

using namespace std;

ifstream f("culori.in");
ofstream g("culori.out");

const int mod = 9901;
const int nmax = 515;
int n, i, j, v[nmax], l, k;
int dp[2*nmax+1][2*nmax+1];

int main() {
    f >> n;
    for (i = 1; i < 2*n; i++)
        f >> v[i];

    for (i = 1; i < 2*n; i++)
        dp[i][i] = 1;

    for (l = 2; l < 2*n-1; l+=2) {
        for (i = 1; i+l < 2*n; i++) {
            j = i+l;
            if (v[i] != v[j]) continue;
            for (k = 1; k < j; k++) {
                if (v[i+1] == v[k]) {
                    dp[i][j] = (dp[i][j] + (dp[i+1][k]*dp[k+1][j])%mod)%mod;
                }
            }
            ;
        }
    }

    g << dp[1][2*n-1];
    return 0;
}