N=int(input())
A=list(map(int,input().split()))+["*"]

X=[]
l=0
k=A[0]
for r in range(N+1):
    if k!=A[r]:
        X.append(r-l)
        k=A[r]
        l=r

K=len(X)
DP=[[0,0] for _ in range(K+1)]

for i in range(1,K+1):
    DP[i][1]=DP[i-1][0]+X[i-1]
    DP[i][0]=max(DP[i-1])
print(max(DP[-1]))