fun Int.k_prime(x: Int): Boolean {
    var n = x
    var f = 0
    var p = 2
    while (f < this && p * p <= n) {
        while (0 == n % p) { n /= p; f++ }
        p++
    }
    return f + (if (n > 1) 1 else 0) == this
}
 
fun Int.primes(n : Int) : List<Int> {
    var i = 2
    var list = mutableListOf<Int>()
    while (true) {
        if (k_prime(i)) { 
          if( i > n ) break
          list.add(i)
        }
        i++
    }
    return list
}

fun main(args:Array<String>) {
  println( 1.primes( readLine()!!.toInt() ).sum() )
}