def sieve(n):
  ass = []
  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
  for i in range(n+1):
    if is_prime[i]:
      ass.append(i)
  return(ass)

n = int(input())
l = sieve(n)
print(sum(l))