n=int(input())
a=[int(j)for j in input().split()]
l=[0,a[0]-a[1]]
for i in range(1,n):
    l.append(l[-1]+a[2*i]-a[2*i+1])
a=a[::-1]
r=[a[0]-a[1]]
for i in range(1,n):
    r.append(r[-1]+a[2*i]-a[2*i+1])
r=r[::-1]+[0]
ans=0
for i in range(n+1):
    ans=max(ans,l[i]+r[i])
print(ans)