from collections import * from itertools import * from functools import * from heapq import * import sys,math input = sys.stdin.readline class prime_factorize(): def __init__(self,M=10**6): self.sieve = [-1]*(M+1) self.sieve[1] = 1 self.p = [False]*(M+1) self.mu = [1]*(M+1) for i in range(2,M+1): if self.sieve[i] == -1: self.p[i] = True i2 = i**2 for j in range(i2,M+1,i2): self.mu[j] = 0 for j in range(i,M+1,i): self.sieve[j] = i self.mu[j] *= -1 def factors(self,x): tmp = [] while self.sieve[x] != x: tmp.append(self.sieve[x]) x //= self.sieve[x] tmp.append(self.sieve[x]) return tmp def is_prime(self,x): return self.p[x] def mobius(self,x): return self.mu[x] N = int(input()) pf = prime_factorize() ans = 0 S = set() P = set() for i in range(2,N+1): if pf.is_prime(i): P.add(i) S.add(i**2) if N==1: print(0) exit() p = 2 for q in P: if (q+2) in S: ans += 1 print(ans*2 - 1)