n = int(input())
if n == 1:
    print(0)
else:
    sum_of_prime = 0
    for i in range(2, n + 1):
        counter = 0
        for j in range(1, i):
            if i % j == 0:
                counter += 1
        if counter == 1:
            sum_of_prime += i
    print(sum_of_prime)