import math

def primes(x):
	input_list=[False if i % 2==0 or i % 3 ==0 or i % 5 == 0 else True for i in range(x)]
	input_list[0] = input_list[1] = False
	input_list[2] = input_list[3] = input_list[5] = True
	sqrt = math.sqrt(x)

	for prime in range(3,x,2):
		if prime>=sqrt:
			break
		if not input_list[prime]:
			continue
		for s in range(prime ** 2,x,prime):
			input_list[s]=False

	return [i for i, b in enumerate(input_list) if b == True]

n = int(input())
prime_list = primes(n+1)
print(sum(prime_list))