#!/usr/bin/env python3

def primes(n):
    sieve = [False] * n
    for p in range(2, n):
        if sieve[p]:
            continue
        for i in range(p**2, n, p):
            sieve[i] = True
    return sieve

bound = 10**6
sieve = primes(bound)
c = 0

n = 1
cube_diff = 7

while cube_diff < bound:
    if not sieve[cube_diff]:
        c += 1
    n += 1
    cube_diff = 3*n**2 + 3*n + 1

print(c)