#include<cstdio>
#define mod 9901
int v[600],dp[600][600];
int main(){
freopen("culori.in","r",stdin);
freopen("culori.out","w",stdout);
int n,i,l,j,k;
scanf("%d",&n);
for(i=1;i<=2*n-1;i++)
scanf("%d",&v[i]);
for(i=1;i<=2*n-1;i++)
dp[i][i]=1;
for(l=2;l<=2*n-2;l=l+2)
for(i=1;i<=2*n-1-l;i++){
j=i+l;
if (v[i]==v[j]){
for(k=i+1;k<j;k++)
if (v[i+1]==v[k])
dp[i][j]=(dp[i][j]+dp[i+1][k]*dp[k+1][j])%mod;}}
printf("%d\n",dp[1][2*n-1]);
return 0;}