#include <stdio.h>
#define NMAX 260

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]) % 9901;
            }

       freopen("culori.out", "w", stdout);
       printf("%d\n", A[1][N]);

        return 0;

}