#include <fstream>
#define mod 9901

using namespace std;

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

int n, m, d[1080][1080], a[1080];

int main()
{
    f>>n; m=2*n-1;
    for (int i=1; i<=m; ++i) f>>a[i], d[i][i]=1;

    for (int l=1; l<=m; ++l)
      for (int i=1; i<=m; ++i)
        if( a[i]==a[i+l] )
          for(int k=i+1; k<i+l; ++k) d[i][i+l]=(d[i][i+l]+d[i+1][k]*d[k+1][i+l])%mod;

    g<<d[1][m]<<'\n';
    f.close(); g.close();
    return 0;
}