fin = open("ciur.in", 'r')
fout = open("ciur.out", 'w')
def prim():
    n = int(fin.readline().strip())
    i = 2
    suma = 0
    while i <= n:
        d = 2
        nr = 0
        while d <= i / 2:
            if i % d == 0:
                nr += 1
            d += 1
        if nr == 0:
            suma += 1
        i += 1
    fout.write(str(suma))
prim()
fin.close()
fout.close()