#include<fstream>
#define DIM 520
using namespace std;
ifstream fin("culori.in");
ofstream fout("culori.out");
int x[DIM],d[DIM][DIM],n,i,j,k,dist;
int main(){
    fin>>n;
    n=2*n-1;
    for(i=1;i<=n;i++){
        fin>>x[i];
        d[i][i]=1;
    }
    for(dist=1;dist<=n;dist++){
        for(i=1,j=dist+i-1 ; j<=n ; j++,i++){
            if(x[i]==x[j]){
                for(k=i+1;k<j;k++)
                    if(x[i+1]==x[k])
                        d[i][j] = (d[i][j] + d[i+1][k] * d[k+1][j]) % 9901 ;
            }
        }
    }
    fout<<d[1][n];
    return 0;
}