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)))