a,b=[],[]

for i in range(int(input())-1):
    c,d=map(int,input().split())
    a.append(c)
    b.append(d)

i = max(b) - sum(a) + a[b.index(max(b))]
d = sum(b)+1
if i < 0:
    i=0

print(d-i)