def prime(a):
    if a == 1:
        return []
    li = [2]
    B = [0, 1] * (a // 2 + 1)
    for i in range(3, a + 1, 2):
        if B[i]:
            li.append(i)
            for j in range(i, a + 1, i):
                B[j] = 0
    return li
def solve():
    n = int(input())
    if n == 1:
        return 0
    pri = prime(n)
    R = set(r * r for r in pri)
    ans = 1
    for p in pri[1:]:
        if p + 2 in R:
            ans += 2
    return ans
print(solve())