N = int(input())
A = list(map(int,input().split()))
_max = 0
for i in range(N):
    _max += -A[i * 2] + A[i * 2 + 1]
now = _max
for i in range(0,N):
    now += 2 * A[i * 2] - 2 * A[i * 2 + 1]
    if now > _max:
        _max = now
print(_max)