def check(a,b,c):
	if a&b&c or ((not b) & (not c)):
		return 0
	return 1

def DP(e,a,b,MOD):
	dp=[[[0 for k in range(2)] for j in range(2)] for i in range(2010)]
	dp[2][a][b]=1
	for i in range(len(e)):
		for j in range(2):
			for k in range(2):
				for l in range(2):
					if check(j,k,l)==e[i]:
						dp[i+1][k][l]+=dp[i][j][k]
						dp[i+1][k][l]%=MOD
	res=0
	for i in range(2):
		for j in range(2):
			if check(i,j,a)==e[0] and check(j,a,b)==e[1]:
				res+=dp[len(e)][i][j]
				res%=MOD

	return res

def main():
	MOD=1e9+7
	n=int(input())
	ls=[[0 for j in range(2)] for i in range(n)]
	e=list()
	for i in range(n):
		e.append(int(input()))
	ans=0;
	for i in range(2):
		for j in range(2):
			ans+=DP(e,i,j,MOD)
			ans%=MOD
	print(int(ans))


if __name__=="__main__":
	main()