import scala.math.sqrt

object Main{
  def main(args: Array[String]){
    val input=io.Source.stdin.getLines().mkString("\n");
    println(solve(input).trim());
  }

  def solve(input:String):String={
    val n = input.toInt;
    Range(2, n+1).toList.filter(isPrime(_)).sum.toString
  }
  
  def isPrime(num:Long):Boolean = {
    if (num ==2 ) {
      true
    } else if (num == 1 || num%2==0) {
      false
    } else {
      (3L to sqrt(num).toLong).filter(
        n => n%2 != 0
      ).foreach { e =>
        if(num%e == 0) return false
      }
      true
    }
  }
}