package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	sum := 0
	for i:=2; i<= n; i++ {
		ok := true
		for k:=i-1; k>1; k-- {
			ok = ok && i%k != 0
		}
		if ok {
			sum += i;
		}
	}
	Println(sum)
}