#include<stdio.h>
#define NMAX 100
#define MOD 9901

int N,n,i,k,l,j,a[NMAX][NMAX],v[NMAX];

int main(){

FILE *f=fopen("culori.in","r");
fscanf(f,"%d",&n);
N=2*n - 1;

  for(i=1;i<=N;i++)
  fscanf(f,"%d",&v[i]);

fclose(f);


  for(i=1;i<=N;i++)
  a[i][i] = 1;


  for(l=3;l<=N;l+=2){
    for(i=1;i<=N;i++){
    j=i+l-1;
      if(v[i] == v[j]){
      a[i][j]=1;

       for(k=i+1;k<j;k++){
       a[i][j]+=a[i][k]*a[k][j];
       a[i][j]%=MOD;
       }

      }

    }
  }

FILE *g=fopen("culori.out","w");
fprintf(g,"%d",a[1][N]);
fclose(g);


return 0;
}