a, b = sorted(map(int, raw_input().split()))
if(a == b or a == 0):
    print 1
elif(a == 1 or (a < b-a)):
    sol = b - a
    n = a + 1
    while n <= (b-a)/2:
        if((b-a) % n == 0):
            sol = n - a
            break
        n = n + 1
    print sol
else:
    print b-a - a%(b-a)