import java.io.BufferedReader
import java.io.InputStreamReader
import java.io.PrintWriter
import kotlin.math.max

object Solve {

  private val br = BufferedReader(InputStreamReader(System.`in`))
  private val out = PrintWriter(System.out)

  fun solve() {

    var (n, x, t) = br.readLine()!!.split(' ').map { it.toInt() }

    out.println(t * (n / x + if (n % x == 0) 0 else 1))
    out.flush()
  }
}

fun main(args: Array<String>) {
  Solve.solve()
}