import kotlin.math.ceil

fun solver(n: Int, x: Int, t: Int): Int {
    val times = ceil(n.toDouble() / x).toInt()

    return times * t
}

fun main(args: Array<String>) {
    val (n, x, t) = readLine()!!.split(" ").map { it.toInt() }

    /*
    val n = 20
    val x = 12
    val t = 6  
     */

    val result = solver(n, x, t)

    println(result)
}
