def prsh(N):
    prime = [2]
    for L in range(3,N):
        for p in prime:
            if not L % p:
                break
            if p > L**(1/2):
                prime.append(L)
                break
    return prime

N = int(input())

ans = 0
if N >= 2:
    ans += 1
plist = prsh(N)
pset = set(plist)
if 2 in pset:
    plist.remove(2)
for p1 in plist:
    if (p1**2 - 2) in pset:
        ans += 2
print(ans)