#include <stdio.h>
#define NMAX 260
#define MOD 9901
int A[4*NMAX][4*NMAX], Val[4*NMAX], N;
int main()
{int l, i, j, k;
freopen("culori.in", "r", stdin);
scanf("%d", &N);
N = 2*N-1;
for (i=1;i<=N;i++)
scanf("%d", &Val[i]);
for (i=1;i<=N;i++) A[i][i] = 1;
for (l=2;l<=N;l++)
for (i=1;i<=N;i++)
{ j=i+l-1;
if (Val[i] == Val[j])
for (k=i+1;k<j;k++)
if (Val[i+1] == Val[k])
A[i][j]=(A[i][j]+(A[i+1][k]*A[k+1][j]))%MOD;}
freopen("culori.out", "w", stdout);
printf("%d\n", A[1][N]); 
return 0; 
}