import math

def is_prime(num):
    if num < 2:
        return False
    sqrt_num = int(math.sqrt(num)) + 1
    for d in range(2, sqrt_num):
        if num % 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)