import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


def sieve_of_eratosthenes(n):  # n以下の素数の全列挙
    prime_list = []
    is_prime = [1]*(n+1)  # A[i] = iが素数なら1,その他は0
    is_prime[0] = is_prime[1] = 0
    for i in range(2,int(n**.5)+1):
        if is_prime[i]:
            prime_list.append(i)
            for j in range(i**2,n+1,i):
                is_prime[j] = 0
    for i in range(int(n**.5)+1,n+1):
        if is_prime[i] == 1:
            prime_list.append(i)
    return is_prime


N = I()
is_prime = sieve_of_eratosthenes(N)

if N == 1:
    print(0)
    exit()

ans = 1
a = 0
for r in range(3,N+1):
    if is_prime[r]:
        p = r**2-2
        if p > N:
            break
        if is_prime[p]:
            a += 1
ans += 2*a
print(ans)