from sys import stdin, stdout

N = int(stdin.readline())

sieve = [True for i in range(N+1)]

p = 2
while( p*p <= N ):
  if sieve[p]:
    for i in range( p*2, N+1, p ):
      sieve[i] = False
  p += 1

result = sum([i for i in range(2,N+1) if sieve[i]])
stdout.write("%d\n" % result)