N = int(input())
sum_A = 0
sum_B = 0
max_AB = 0
for _ in range(N-1):
    A, B = map(int, input().split())
    sum_A += A
    sum_B += B
    max_AB = max(max_AB, A + B)
ans = min(sum_A, sum_B) - max(0, max_AB - max(sum_A, sum_B)) + 1
print(ans)