n = int(input())
import math

def sieve(n):
    ass = []
    is_prime = [True]*(n+1)
    is_prime[0] = False
    is_prime[1] = False

    for i in range(2, int(math.sqrt(n))+1):
        if not is_prime[i]:
            continue
        for j in range(i*2, n+1, i):
            is_prime[j] = False
    for i in range(n+1):
        if is_prime[i]:
            ass.append(i)
    return(ass)

S = sieve(n)
T = set()
for s in S:
    T.add(s**2)
ans = 0
for q in S:
    if q+2 in T:
        if q != 2:
            ans += 2
        else:
            ans += 1
print(ans)