fun main() = Thread(null, ::abc172d, "(^o^)", 128 * 1024 * 1024).apply { start() }.join()

@OptIn(ExperimentalStdlibApi::class)
fun abc172d() {
    val k = readLine()!!.toLong()

    val divCount = LongArray(k.toInt() + 1)

    for (i in 1..k) {
        var num = 1
        while (num <= k / i) divCount[(num++ * i).toInt()]++
    }

    val answer = (1..k).map {
        it * divCount[it.toInt()]
    }.sum()

    println(answer)
}
