def Eratosthenes(n):
    is_prime=[True] * (n+1)
    is_prime[0]=False
    is_prime[1]=False
    for i in range(2,int(n**0.5)+1):
        if not is_prime[i]:
            continue
        for j in range(i*2,n+1,i):
            is_prime[j]=False
    return [i for i in range(n+1) if is_prime[i]]
n=int(input())
l=Eratosthenes(n)
ans=0
l=set(l)
for i in l:
    if i*i-2 in l:
        ans+=1
ans*=2
if n>=2:
    ans-=1
print(ans)