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

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