import Foundation

func isPrime(_ n:Int) -> Bool{
    if n == 1{return false}
    if n != 2 && n % 2 == 0{return false}
    var c = 3
    while c <= 1 + Int(sqrt(Double(n))){
        if n % c == 0{
            return false
        }else{
            c += 2
        }
    }
    return true
}

let n = Int(readLine()!)!
var c = 0
for i in 1...n{
    if isPrime(i){
        c += i
    }
}
print(c)