import sys

sys.setrecursionlimit(10**6)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
md = 998244353
# md = 10**9+7

mx = 500001

isprime = [True]*mx
isprime[0] = isprime[1] = False
pp = []
for a in range(2, mx):
    if isprime[a]:
        pp.append(a)
        for b in range(a**2, mx, a):
            isprime[b] = False

n = II()
if n == 1:
    print(0)
    exit()

ans = 1
for r in pp[1:]:
    p = r**2-2
    if r > n or p > n: break
    if isprime[p]:
        ans += 2

print(ans)