import java.util.*


var MAX = 10000001
var factor = IntArray(10000001)

fun main(args: Array<String>) {
    val scan = Scanner(System.`in`)
    var kotlin=scan.nextLine().toInt()
    var ans : Long = 0
    generatePrimeFactors()
    for(i in 1..kotlin)
        ans+= (i*calculateNoOFactors(i))
    println(ans)
}

fun generatePrimeFactors() {
    factor[1] = 1
    for (i in 2 until MAX)
        factor[i] = i

    run {
        var i = 4
        while (i < MAX) {
            factor[i] = 2
            i += 2
        }
    }

    var i = 3
    while (i * i < MAX) {

        if (factor[i] == i) {
            var j = i * i
            while (j < MAX) {
                if (factor[j] == j) factor[j] = i
                j += i
            }
        }
        i++
    }
}

fun calculateNoOFactors(n: Int): Long {
    if (n == 1) return 1
    var ans : Long = 1

    var dup = factor[n]
    var c = 1
    var j = n / factor[n]
    while (j != 1) {
        if (factor[j] === dup) c += 1 else {
            dup = factor[j]
            ans = ans * (c + 1)
            c = 1
        }

        j = j / factor[j]
    }

    ans = ans * (c + 1)
    return ans
}