p=[True]*(1000)
p[0]=False; p[1]=False
i=2
while i<len(p):
  if p[i]==False: i+=1; continue
  j=2
  while i*j<len(p):
    p[i*j]=False
    j+=1
  i+=1
N=int(input())
# print(p)

ans=1
count=0

for i in range(len(p)):
  if p[i] and ans*i<=N:
    ans*=i
    count+=1
  elif not p[i]:
    continue
  else:
    print(count)
    exit()