N = int(input())
A, B = 0, 0
AB = []
for _ in range(N-1):
    a, b = map(int, input().split())
    AB.append((a, b))
    A += a
    B += b

if A > B:
    l = 0
    for a, b in AB:
        l = max(l, b-A)
    ans = B-l+1
elif A < B:
    l = 0
    for a, b in AB:
        l = max(l, a-B)
    ans = A-l+1
else:
    l, r = 0, 0
    for a, b in AB:
        l = max(l, b-A)
        r = max(r, a-B)
    ans = A - max(l, r) + 1
print(ans)