#include <stdio.h>
#include <string.h>

#define MAXN 512
#define MOD 9901

int N, C[MAXN];
int A[MAXN][MAXN];

int main(void)
{
    freopen("culori.in", "rt", stdin);
    freopen("culori.out", "wt", stdout);

    int i, j, k, r, M;

    scanf("%d\n", &N);

    M = 2*N-1;
    
    for(i = 1; i <= 2*N-1; i++)
        scanf("%d ", &C[i]);

    for(i = M; i >= 1; i--)
     for(A[i][i] = 1, j = i+1; j <= M; j++)
     {
        r = 0;
        for(k = i+2; k <= j; k++)
         if(C[i] == C[k] && C[k] == C[j])
            r += A[i+1][k-1]*A[k][j], r %= MOD;
        A[i][j] = r;
     }
     
    printf("%d\n", A[1][M]);

    return 0;
}