N=int(input())
if N<3:	print(N-1);exit()
rn=int(N**0.5)+2
k,*pa=[n for n in range(3,N+1,2)]
pr=[]
while k<rn:
	pr+=[k]
	pa=[n for n in pa if n%k>0]
	k=pa[0]
pa=pr+pa
cn=0
for r in pr:
	if r*r-2 in pa:	cn+=1
print(cn*2+1)