import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    }

} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    }

} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    } main {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int x = sc.nextInt(); x sc.nextInt() sc.nextInt sc int t = sc.nextInt(); t sc.nextInt() sc.nextInt sc int res = (n + (x-1)) / x * t; res (n + (x-1)) / x * t (n + (x-1)) / x (n + (x-1)) n (x-1) x 1 x t System.out.println(res) System.out.println System.out System System.out res String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    }

} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    }

} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int res = (n + (x-1)) / x * t;
        System.out.println(res);
    }

}