def gcd(a, b):
    while b:      
        a, b = b, a % b
    return a

def lcm(a, b):
    return a * b // gcd(a, b)

def factorize(n):
    factors=[]
    for i in range(1, n+1):
        if(n % i == 0):
            factors.append(i)
    return factors

a, b = sorted(map(int, raw_input().split()))
if(a == b or a == 0):
    print 1
elif(a == 1 or (a < b-a)):
    factors = factorize(b-a)
    for i in factors:
        if(a < i):
            print i - a
            break
else:
    print b-a - a%(b-a)