# verification-helper: PROBLEM https://yukicoder.me/problems/no/713

def primes(n: int) -> list:
    "素数の列挙を行う"

    is_prime = [True] * (n + 1)
    is_prime[0] = False
    is_prime[1] = False

    for i in range(2, int(n ** 0.5) + 1):
        if not is_prime[i]:
            continue
        for j in range(i * 2, n + 1, i):
            is_prime[j] = False

    return [i for i, j in enumerate(is_prime) if j]


def main() -> None:
    print(sum(primes(int(input()))))


if __name__ == "__main__":
    main()