ans = 0
def prime_judge(num):
    p=2
    ans=True
    while p <= num**(1/2):
        if num%p == 0:
            ans=False
            break
        p += 1
    return ans

A, B = (int(x) for x in input().split())
for i in range(A, B+1):
    if prime_judge(i):
        ans += i*i*i-i*i+i+1

print(ans)