#include <bits/stdc++.h>
#define Nmax 1030
#define MOD 9901
using namespace std;
ifstream f("culori.in");
ofstream g("culori.out");
int pd[Nmax][Nmax];
int v[Nmax];
int main()
{
    int n,N;
    f>>N;
    n=2*N-1;
    int i,j,k;
    for(i=1;i<=n;i++)
    {
        f>>v[i];
        pd[i][i]=1;
    }
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
            if(v[i+j]==v[j])
                for(k=j+1;k<=i+j;k++)
                    pd[j][i+j]=(pd[j][i+j]+(pd[j+1][k]*pd[k+1][i+j])%MOD)%MOD;
    g<<pd[1][n];

    return 0;
}