def primes(n):
    memo = [True] * (n + 1)
    i = 2
    while i * i <= n:
        if memo[i]:
            j = i << 1
            while j <= n:
                memo[j] = False
                j += i
        i += 1
    return [i for i in range(n + 1) if memo[i] and i >= 2]

N = int(input())
print(sum(primes(N)))