L,R = map(int, input().split())
count = 0

import math

def is_prime(n):
    if n == 1: return False

    for k in range(2, int(math.sqrt(n)) + 1):
        if n % k == 0:
            return False

    return True

for i in range(L-1,R):
    for j in range(i,R):
        s = i+1
        for k in range(i+1,j+1):
            s += (k+1)
        if is_prime(s) == True:
            count += 1

print(count)