N = int(input())

def sieve_of_eratosthenes(n):
    # https://af-e.net/python-sieve-of-eratosthenes/
    primes = [True] * (n + 1)
    p = 2
    while (p * p <= n):
        if primes[p]:
            for i in range(p * p, n + 1, p):
                primes[i] = False
        p += 1
    return [p for p in range(2, n + 1) if primes[p]]

ps = sieve_of_eratosthenes(int(N**(1/2))+100)
ans = 0
for p in ps:
    for exp in range(2,60):
        if(p**exp <= N):
            ans += p**exp
        else:
            break
print(ans)