#include <stdio.h>
#include <stdlib.h>
#define MOD 9901
#define MAXN 256
int v[2*MAXN],mat[2*MAXN][2*MAXN];
int main(){
    FILE*fi,*fout;
    int i,j,n,k,x;
    fi=fopen("culori.in" ,"r");
    fout=fopen("culori.out" ,"w");
    fscanf(fi,"%d" ,&n);
    for(i=1;i<2*n;i++){
        fscanf(fi,"%d" ,&v[i]);
        mat[i][i]=1;
    }
    for(x=2;x<2*n-1;x++)
        for(i=1;i+x<2*n;i++){
            j=i+x;
            if(v[i]==v[j])
               for(k=i+1;k<j;k++)
                if(v[k]==v[i+1])
                  mat[i][j]=(mat[i][j]+mat[i+1][k]*mat[k+1][j])%MOD;
        }
    fprintf(fout,"%d" ,mat[1][2*n-1]);
    fclose(fi);
    fclose(fout);
    return 0;
}