import math

def is_prime(n):
    if n == 1: return False

    for k in range(2, int(math.sqrt(n)) + 1):
        if n % k == 0:
            return False

    return True

a = int(input())
b = []
for x in range(a+1):
	if is_prime(x) == True:
		b.append(x)

print(sum(b))