#include <bits/stdc++.h>

#define MOD 9901
using namespace std;

int n, k, v[520], dp[520][520], l, j;

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

int main ()
{
    fin>>n;
    n=2*n-1;
    for(int i=1;i<=n;++i)
        fin>>v[i];
    for(int i=1;i<=n;++i)
        dp[i][i]=1;
    for(int l=1;l<=n;++l)
    {
        for(int i=1;i<=n-l+1;++i)
        {
            j=i+l-1;
            if(v[i]==v[j]&&(i+j)%2==0)
            for(int k=i+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;
        }
    }
    fout<<dp[1][n];
    return 0;
}