def isp(x):
    if x <= 1:
        return False
    if x == 2:
        return True
    for i in range(2, int(x ** 0.5) + 2):
        if x % i == 0:
            return False
    return True
N = int(input())
ans = 0
for i in range(2, N + 1):
    if isp(i):
        ans += i
print(ans)