import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
A=[int(i) for i in input().split()]
B=[[0]*2 for _ in range(n+1)]
for i,a in enumerate(A):
  B[i+1][0]=max(B[i])
  B[i+1][1]=B[i][0]+A[i]
print(max(B[n]))