#include<cstdio>
#define MOD 9901
int n,i,j,k,l,v[1100],x[1100],d[1100][1100];
FILE *f,*g;
int main(){
    f=fopen("culori.in","r");
    g=fopen("culori.out","w");
    fscanf(f,"%d",&n);
    n=2*n-1;
    for(i=1;i<=n;i++){
        fscanf(f,"%d",&v[i]);
        d[i][i]=1;
    }
    for(l=3;l<=n;l+=2){
        for(i=1;i+l-1<=n;i++){
            j=i+l-1;
            if(v[i]==v[j]){
                for(k=i+1;k<=j;k++){
                    d[i][j] = ( d[i][j] + ( d[i+1][k] * d[k+1][j] ) % MOD ) % MOD;
                }
            }
        }
    }
    fprintf(g,"%d",d[1][n]);



    fclose(f);
    fclose(g);
    return 0;
}