def isPrime (n):
	if n == 1 or (n != 2 and n % 2 == 0):
		return False
	d = 3
	while d * d <= n:
		if n % d == 0:
			return False
		d += 2
	
	return True

N = int(input())
ans = 0
for i in range(N + 1):
	if isPrime(i):
		ans += i

print(ans)