def sieve(n):
    is_prime = [True for _ in range(n+1)]
    is_prime[0] = False

    for i in range(2, n+1):
        if is_prime[i-1]:
            j = 2 * i
            while j <= n:
                is_prime[j-1] = False
                j += i
    table = [ i for i in range(1, n+1) if is_prime[i-1]]
    return is_prime, table

n = int(input())
is_prime,t = sieve(n-1)
ans = 0
for i in range(len(t)):
    for j in range(len(t)):
        t = p[i] * p[i] - p[j]
        if (t < 1 or t > N):
            break
        if (is_prime[t]):
            ans += 1
print(ans)