n=int(input())
p=[2]
for i in range(3,n+1):
    for j in p:
        if j*j>i:
            p.append(i)
            break
        if i%j==0:
            break
s=set(p)
ans=1
for i in p[1:]:
    if i*i-2 in s:
        ans+=2
print(ans)