import sys input=lambda: sys.stdin.readline().rstrip() n=int(input()) def primes(n): is_prime=[True]*(n+1) is_prime[0]=False is_prime[1]=False for i in range(2,int(n**0.5)+1): if not is_prime[i]: continue for j in range(i*2,n+1,i): is_prime[j]=False return [i for i in range(n+1) if is_prime[i]] print(sum(primes(n)))