def eratosthenes(n):
    is_prime = [False, False] + [True] * (n-1)
    for p in range(2, n+1):
        if not(is_prime[p]):
            continue
        for k in range(p*2, n+1, p):
            is_prime[k] = False
    return is_prime

import math
N=int(input())
pr = eratosthenes(math.isqrt(N)+1)
ans=0
for i in range(1,len(pr)):
    if pr[i]:
        tmp = i
        while tmp <= N:
            tmp*=i
            if tmp <= N:
                ans+=tmp
print(ans)