from collections import deque

N, *A = map(int, open(0).read().split())

ans = 0
Q = deque(zip(*[iter(A)] * 2))
while Q:
    lh, lt = Q[0]
    l = lh - lt
    rt, rh = Q[-1]
    r = rh - rt

    if l < r:
        Q.pop()
    else:
        Q.popleft()

    ans += max(l, r)

print(ans)