#include<fstream>
using namespace std;
ifstream f("culori.in");
ofstream g("culori.out");
int n,m,i,j,k,c[600],a[1<<10][1<<10];
int main()
{
    f>>n;
    m=2*n-1;
    for(i=1;i<=m;++i)
    {
        f>>c[i];
        a[i][i]=1;
    }
    for(i=1;i<=m;++i)
        for(j=1;j<=m;++j)
            if(c[i+j]==c[j])
                for(k=j+1;k<=min(i+j,m);++k)
                    a[j][i+j]=(a[j][i+j]+a[j+1][k]*a[k+1][i+j])%9901;
    g<<a[1][m];
    return 0;
}