#include<fstream>
#define mod 9901
using namespace std;


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

int main (){
	
	f>>n;
	n=2*n-1;
	for(i=1;i<=n; ++i){
		f>>v[i];
		A[i][i]=1;
	}
	
	for( l =1 ;l<=n; l++  ) {
		
		for(i=1 ; i+l<n; ++i){
			
			j=i+l-1;
			if(v[i]==v[j])
				for(k=i+1 ;k<=j; k++)
					A[i][j]+=(A[i][k-1]*[k][j])%mod;
		}
	}
 	
	return 0;
}