sosu = [True]*(10**6+100+5)
sosu[0],sosu[1] = False,False
for i in range(2,10**6+100+1):
    if sosu[i]:
        for j in range(2,10**6):
            if i*j > 10**6:
                break
            else:
                sosu[i*j] = False

sosu2 = []

for i,v in enumerate(sosu):
    if v:
        sosu2.append(i)

N = int(input())
ans = 1
for i,v in enumerate(sosu2):
    if ans * v > N:
        print(i)
        exit()
    else:
        ans *= v