#include<stdio.h>
#define nmax 600
#define nrm 600
#define ko 9901
long a[nmax][nmax],s[nrm],n;

long rezolva()
{long i,l,k;
 for(i=1;i<=2*n-1;i++)
  if(s[i]==s[i+2])
	a[i][i+2]=1;

 for(l=4;l<2*n-1;l+=2)
	for(i=1;i<=2*n-1;i++)
	 if(s[i]==s[i+l])
	  {a[i][i+l]++;
	   for(k=i+2;k<i+l&&k<=2*n-1;k+=2)
	   if(s[k]==s[i])
		 {
		  a[i][i+l]=(a[i][i+l]+a[i][k]*a[k][i+l])%ko;
		  }
	   }
 return a[1][2*n-1];
 }





int main()
{int i;
 freopen("culori.in","r",stdin);
 scanf("%ld",&n);
 for(i=1;i<=2*n-1;i++)
  scanf("%ld",&s[i]);

 freopen("culori.out","w",stdout);
 printf("%ld",rezolva());
 fclose(stdout);
 return 0;
 }