n = int(input())
a,b,c= 0, 0, 0
d = []
for i in range(n):
    a,b = [int(x) for x in input().split()]
    c = b % a
    if c > 0:
        d.append(c)
b = 0
for i in range(len(d)):
    if d.count(d[i]) >= b and d[i] > c:
        b = d.count(d[i])
        c = d[i]
print(c)