from sys import stdin, stdout
input = lambda: stdin.readline().rstrip()
write = stdout.write

def main():
    N = int(input())

    if N == 1:
        print(0)
        return

    lst = erastosthenes(N)
    prime_list = [2] + [i for i in range(3, N + 1, 2) if lst[i]]
    print(sum(prime_list))

def erastosthenes(n):
    prime = [0, 1] * ((n + 1) // 2)
    if not n % 2:
        prime += [0]
    prime[1], prime[2] = 0, 1

    sqrt = n ** 0.5
    i = 3
    while i <= sqrt:
        for j in range(i ** 2, n + 1, i):
            prime[j] = 0
        i += 2
    return prime

main()