import java.lang.reflect.Array;
import java.util.*;
import java.io.*;
import java.lang.*;

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

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

        if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t);
    }
} import java.lang.reflect.Array; Array java.lang.reflect import java.util.*; util.* java import java.io.*; io.* java import java.lang.*; lang.* java public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

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

        if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t);
    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

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

        if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t);
    } main {
        Scanner sc = new Scanner(System.in);

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

        if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t);
    } 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 if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t); n%x == 0 n%x n x 0 System.out.println((n/x)*t) System.out.println System.out System System.out (n/x)*t (n/x) n x t System.out.println(((n/x)+1)*t) System.out.println System.out System System.out ((n/x)+1)*t ((n/x)+1) (n/x) n x 1 t String[] args args public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

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

        if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t);
    }
} public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

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

        if (n%x == 0)
            System.out.println((n/x)*t);
        else
            System.out.println(((n/x)+1)*t);
    }
} Main
import java.lang.reflect.Array;
import java.util.*;
import java.io.*;
import java.lang.*;

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

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

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