import random
def MillerRabin(n,k=20):
  if n==2:return True
  if n<2 or n%2==0:return False
  s,d=0,n-1
  while d&1==0:
    s+=1
    d>>=1
  for _ in range(k):
    a=random.randint(1,n-1)
    x=pow(a,d,n)
    if x!=1 and x!=n-1:
      for __ in range(s):
        x=pow(x,2,n)
        if x==n-1:break 
      else:return False
  return True

n=int(input())
primes=[True]*(n+1)
primes[0]=primes[1]=False
for p in range(2,n+1):
  if primes[p]:
    for q in range(2*p,n+1,p):
      primes[q]=False

ans=1
for r in range(3,n):
  if r*r-2>n:break
  if primes[r] and primes[r*r-2]:
    ans+=2

print(ans if n>1 else 0)