import java.util.*;

public class Main {

    public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    }
} import java.util.*; util.* java public class Main {

    public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    }
} Main public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    } main {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan int x = scan.nextInt(); x scan.nextInt() scan.nextInt scan int t = scan.nextInt(); t scan.nextInt() scan.nextInt scan int a = n / x; a n / x n x int b = n % x; b n % x n x if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        } b != 0 b 0 {
            System.out.println(t * (a + 1));
            
        } System.out.println(t * (a + 1)) System.out.println System.out System System.out t * (a + 1) t (a + 1) a 1 {

            System.out.println(t * a);
            
        } System.out.println(t * a) System.out.println System.out System System.out t * a t a String args[] args public class Main {

    public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    }
} public class Main {

    public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    }
} Main
import java.util.*;

public class Main {

    public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    }
}