func readThreeInts(separator: String.Element = " ") -> (a: Int, b: Int, c: Int) {
    let ints = readLine()!.split(separator: separator).map { Int($0)! }
    return (a: ints[0], b: ints[1], c: ints[2])
}

func mainA() {
    let (N, X, T) = readThreeInts()

    let full = N / X
    let remain = N % X

    print(full * T + (remain == 0 ? 0 : T))
}
mainA()