#coding: utf-8
  
def judge_prime(i):
  t = 2
  jud = 0
  while t < i:
    if not i % t == 0:
      t += 1
    else:
      jud = 1
      break
  return 0 if jud == 1 else  i


def prime_list(num):
  num = int(num)
  p_list = []
  for p in range(2, num + 1):
    p_list.append(judge_prime(p))
  return p_list

def sum_list(l):
  return sum(l)


def main():
  p_list = prime_list(input())
  print(sum_list(p_list))

if __name__ == '__main__':
  main()