def prime(n)
  r = []
  a = Array.new(n+1,true)
  for i in 2..[36,n].min
    if a[i]
      r << i
      for j in 1..n/i
        a[i*j] = false
      end
    end
  end
  for i in [36,n].min..n
    if a[i]
      r << i
    end
  end
  r
end

x = gets.to_i
p = prime(x)
ans = 0
b = 0
e = p.size-1
while b <= e
  if p[b]*p[e] > x
    ans += p[e]
    e -= 1
  else
    temp = 1
    while temp <= x
      temp *= p[b]
    end
    if temp/p[b]+p[e] < p[b]*p[e]
      ans += p[b]*p[e]
      e -= 1
    else
      ans += temp/p[b]
    end
    b += 1
  end
end
p ans