#include <cstdio>
#define MOD 9901
using namespace std;
int a[520][520],v[520];
int main()
{
    FILE *fin=fopen ("culori.in","r");
    FILE *fout=fopen ("culori.out","w");
    int n,i,j,k;
    fscanf (fin,"%d",&n);
    for (i=1;i<=2*n-1;i++)
        fscanf (fin,"%d",&v[i]);
    // d[i][j] = nr de arbori care pot genera secv i..j
    for (i=1;i<=2*n-1;i++)
        a[i][i]=1;
    for (i=2*n-3;i>0;i--){
        for (j=2*n-1;j>=i+2;j--){
            if (v[i]!=v[j] || (i+j)%2==1)
                continue;
            for (k=i+1;k<j;k++){
                if (v[i+1]==v[k])
                    a[i][j]=(a[i][j]+(a[i+1][k]*a[k+1][j])%MOD)%MOD;
            }
        }
    }
    fprintf (fout,"%d",a[1][2*n-1]);
    return 0;
}