#include <stdio.h>

#define MAX_N 256
#define FIN "culori.in"
#define FOUT "culori.out"
#define MOD 9901

int N, C[MAX_N<<1], A[MAX_N<<1][MAX_N<<1];

int main(void)
{
    int i, j, k, l;

    freopen(FIN, "r", stdin);
    freopen(FOUT, "w", stdout);

    scanf("%d", &N);
    for (i = 0; i < 2*N-1; i++) scanf("%d", C+i);

    for (i = 0; i < 2*N-1; i++)
        A[i][i] = 1;
    for (i = 0; i+2 < 2*N-1; i++)
        A[i][i+2] = C[i] == C[i+2];
    for (l = 4; l < 2*N-1; l += 2)
        for (i = 0; i+l < 2*N-1; i++)
        {
            j = i+l;
            for (k = i+1; k < j; k++)
            {
                A[i][j] += (C[i] == C[k+1] && C[i+1] == C[k])*A[i+1][k]*A[k+1][j]; 
                A[i][j] %= MOD;
            }
        }

    printf("%d\n", A[0][2*N-2]);

    return 0;
}