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

A = [(0, 0)]
for i in range(N):
    aa, bb = A[-1]
    A.append((aa+X[2*i], bb+X[2*i+1]))
#print(A)
aa, bb = 0, 0
r = -10**18
for i in range(N-1, -1, -1):
    b, a = X[2*i], X[2*i+1]
    r = max(r, A[i+1][0]-A[i+1][1]+aa-bb)
    aa += a
    bb += b

r = max(r, A[0][0]-A[0][1]+aa-bb)
print(r)