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

V = []
for i in range(0, 2 * N, 2):
    a = A[i]
    b = A[i + 1]
    V.append(a - b)

S = sum(V)
ma = S
for i in range(N - 1, -1, -1):
    S -= 2 * V[i]
    ma = max(ma, S)
print(ma)