n = int(input())
tf = [True] * (n + 1)
tf[0] = tf[1] = False
for i in range(int(n ** (1 / 2)) + 1):
  if tf[i]:
    for j in range(i ** 2, n + 1, i):
      tf[j] = False

print(sum([i for i in range(n + 1) if tf[i]]))