n = int(input())
def prime(n):
    NP = [True for _ in range(n+1)]
    P = []
    for i in range(2, n+1):
        if NP[i]:
            P.append(i)
            for j in range(i, n+1, i):
                NP[j] = False
    return P
P = prime(10**5)
ans = 0
for i in range(len(P)):
    p = P[i]
    if p * p > n:
        break
    now = p * p
    while now <= n:
        ans += now
        now *= p
print(ans)