#include<fstream>
#define dim 2*257
using namespace std;
ifstream cin("culori.in");
ofstream cout("culori.out");
int c[dim],d[dim][dim],n,m,i,j,k,l;
int main()
{
    cin>>n;
    for(i=1;i<2*n;i++)
        cin>>c[i];
    m=2*n-1;
    for(i=1;i<=m;i++){
        d[i][i]=1;
    }
    for(l=3;l<=m;l+=2){
        for(i=1;i+l-1<=m;i++){
            j=i+l-1;
            if(c[i]==c[j]){
                for(k=i+1;k<=j;k++){
                    d[i][j]+=(d[i+1][k]*d[k+1][j]);
                    d[i][j]%=9901;
                }
            }
        }
    }
    cout<<d[1][m]%9901;
}