def is_prime(n):
    if n <= 1:
        return False
    if n == 2:
        return True
    if n % 2 == 0:
        return False
    max_divisor = int(n ** 0.5) + 1
    for d in range(3, max_divisor, 2):
        if n % d == 0:
            return False
    return True

N = int(input())
sum_primes = 0
for i in range(2, N + 1):
    if is_prime(i):
        sum_primes += i
print(sum_primes)