n = int(input())
IsPrime = [True for _ in range(n + 1)]
IsPrime[0] = IsPrime[1] = False
for i in range(2, n + 1):
    if IsPrime[i]:
        for j in range(i + i, n + 1, i):
            IsPrime[j] = False

Primes = []
Prime_square_set = set()
for i in range(n + 1):
    if IsPrime[i]:
        Primes.append(i)
        Prime_square_set.add(i**2)
ans = 0
for p in Primes:
    if p + 2 in Prime_square_set:
        if p == 2:
            ans += 1
        else:
            ans += 2
print(ans)