R=range
J=lambda:list(map(int,input().split()))
N,*_=J()
P=J()
Q=[[0]*(N+1)for i in R(4)]
for r in R(3):
	for i in R(N):Q[r+1][(Q[r][i+1]^(r<2))*P[i]]=1
print(sum(Q[3][1:]))