fun main(args: Array<String>) {
    val nxt = nextIntList()

    val min = Math.ceil((nxt[0]/nxt[1]).toDouble()).toInt()
    val c = nxt[0]%nxt[1]

    println(min*nxt[2] + if(c == 0)0 else nxt[2])

}
fun next() = readLine()!!
fun nextIntList() = next().split(" ").map{ it.toInt() }