import sys

N=int(input())
A=list(map(int,input().split()))

X=[]
I=0
while I<N:
    J=I
    while J<N and A[I]==A[J]:
        J+=1
    X.append(J-I)
    I=J

print(X,file=sys.stderr)

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]))