#include<stdio.h>
#define NMAX 512

int V[NMAX],D[NMAX][NMAX];

int main()
{
    freopen("culori.in","r",stdin);
    freopen("culori.out","w",stdout);
    
    int N;
    scanf("%d",&N);
    N<<=1;--N;
    
    int i;
    for(i=0; i<N; ++i)
    {
             scanf("%d",&V[i]);
             D[i][i]=1;
    }
    
    int gap,j,k;
    
    for(gap=1; gap<N; ++gap)
    {
               for(i=0; i+gap<N; ++i)
               {
                        j=i+gap;
                        
                        if( V[i]==V[j] && (i+j)%2==0 )
                        {
                            for(k=i+1; k<=j; ++k)
                            {           
                                       D[i][j]+=(D[i+1][k]*D[k+1][j])%9901;
                            }
                        }
                        D[i][j]%=9901;
               }
    }
    
    printf("%d\n",D[0][N-1]);
    return 0;   
}