N = int(input())
def is_prime(n):
    if n == 2: return True
    if n < 2 or n%2 == 0: return False
    m = 3
    while m*m <= n:
        if n%m == 0: return False
        m += 2
    return True

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