import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    }    
} import java.util.Scanner; Scanner java.util public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    }    
} Main static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    } main {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    } int n = sc.nextInt() n sc.nextInt() sc.nextInt sc x = sc.nextInt() x sc.nextInt() sc.nextInt sc t = sc.nextInt(); t sc.nextInt() sc.nextInt sc int ans = n/x + Math.min(n%x , 1); ans n/x + Math.min(n%x , 1) n/x n x Math.min(n%x , 1) Math.min Math n%x n x 1 System.out.println(ans*t) System.out.println System.out System System.out ans*t ans t String[] args args public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    }    
} public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    }    
} Main
import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*t);
    }    
}