#include<fstream>

using namespace std;

const char iname[]="culori.in";
const char oname[]="culori.out";
const int maxn=505;
const int mod=9901;

ifstream f(iname);
ofstream g(oname);

int a[maxn],dp[maxn][maxn],i,j,n,k;

int main()
{
    f>>n;
    n=n*2-1;
    for(i=1;i<=n;++i)
        f>>a[i],dp[i][i]=1;
    for(i=1;i<n;++i)
        for(j=n-i;j;--j)
            if(a[j+i]==a[j])
                for(k=j+1;k<j+i;++k)
                    if(a[k]==a[j+1])
                        dp[j][j+i]=(dp[j][j+i]+dp[j+1][k]*dp[k+1][j+i])%mod;
    g<<dp[1][n]<<"\n";
}