#include<cstdio>
int n,i,j,DP[1010][1010],C[1010],k;
int main()
{
    freopen("culori.in","r",stdin);
    freopen("culori.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=2*n-1;i++){scanf("%d",&C[i]);DP[i][i]=1;}
    for(i=2;i<=2*n-1;i++)
        for(j=i-1;j>=1;j--)
        {
            if(C[i]!=C[j])continue;
            for(k=j+1;k<i;k++)DP[j][i]=(DP[j][i]+DP[j+1][k]*DP[k+1][i])%9901;
        }
    printf("%d",DP[1][2*n-1]);
    return 0;
}