def sieve_of_eratosthenes(n):
    sieve = [True for _ in range(n + 1)]
    sieve[0:1] = [False, False]

    for i in range(2, n + 1):
        if sieve[i]:
            for j in range(2 * i, n + 1, i):
                sieve[j] = False

    primes = []
    for i in range(2, n + 1):
        if sieve[i]:
            primes.append(i)
    return primes


def main():
    n = int(input())
    print(sum(sieve_of_eratosthenes(n)))


if __name__ == "__main__":
    main()