from itertools import product as p

def is_prime(n):
    d = 2
    while d * d <= n and n % d != 0:
        d += 1
    return d * d > n

def get_total_primes(a, b):
    c=0
    for j in range(len(str(a)),len(str(b))+1):
        for i in p('2357',repeat = j):
            q = int(''.join(i))
            if a<=q<b and is_prime(q):
                c+=1
    return c