def f(n):
    global i,lst
    if i % n == 0:
        lst.append(n)
    if n == 1:
        return
    return f(n - 1)

l,j = map(int,input().split())
sum = 0

for i in range(l,j + 1):
    lst = []

    f(i)

    if len(lst) == 2:
        sum += i
    else:
        continue

print(sum)