n=int(input())
L=list(range(n))
s=set()
for i in L:
	if L[i]<2:continue
	L[::i]=[0]*(n//i+(n%i>0))
	s.add(i)
	
c=0
a=set()
for p in s:
	if p*p-2 in s: c+=2
print(c-1)