n = int(input())
if n ==1:
    print(0)
    import sys
    sys.exit()

a = {i for i in range(2, n+1)}
import math
q=set()
while True:
    p=sorted(list(a.difference(q)))[0]
    if p > int(math.sqrt(n)):
        break
    q.add(p)
    for i in range(2,n//p+1):
        a.discard(p*i)
print(sum(a))