import java.io.*;

class Main {
    BufferedReader bf;
    PrintWriter writer;
    StringBuilder sb;
    static boolean local_system = false;

    void run() throws IOException {
        int[] c = ni();
        int d = c[0] % c[1] == 0 ? c[0] / c[1] : c[0] / c[1] + 1;
        writer.println(d*c[2]);
    }

    public static void main(String[] args) throws IOException {
        long start_time = System.currentTimeMillis();
        Main obj = new Main();
        obj.run();
        long end_time = System.currentTimeMillis();
        if (local_system) obj.writer.println("Time : " + (end_time - start_time));
        obj.close();
    }

    public Main(){
        writer = new PrintWriter(System.out);
        bf = new BufferedReader(new InputStreamReader(System.in));
        sb = new StringBuilder();
    }

    public int i() throws IOException {
        return Integer.parseInt(bf.readLine());
    }

    public long l() throws IOException {
        return Long.parseLong(bf.readLine());
    }

    public int[] ni() throws IOException {
        String[] data = bf.readLine().split(" ");
        int[] send = new int[data.length];
        for (int i = 0, h = data.length; i < h; i++) send[i] = Integer.parseInt(data[i]);
        return send;
    }

    public long[] nl() throws IOException {
        String[] data = bf.readLine().split(" ");
        long[] send = new long[data.length];
        for (int i = 0, h = data.length; i < h; i++) send[i] = Long.parseLong(data[i]);
        return send;
    }

    public void close() throws IOException{
        writer.flush();
        writer.close();
        bf.close();
    }
}



/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz