a, b = sorted(map(int, raw_input().split()))

if a==b:
    print 1
elif a < b-a:
    # need a divisor of (b-a)
    # greater than a

    sol = 10**20

    div = 1
    while div * div <= b-a:
        if (b-a) % div == 0:
            if div > a:
                sol = min(sol, div)
            if (b-a)//div > a:
                sol = min(sol, (b-a)//div)
        div += 1

    print max(1, sol-a)
else:
    print (b-a) - a%(b-a)