import java.util.*;

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();
        int res = (n/x)*t;
        if (n % x > 0){
            res += t;
        }
        System.out.println(res);
    }
} import java.util.*; util.* 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();
        int res = (n/x)*t;
        if (n % x > 0){
            res += t;
        }
        System.out.println(res);
    }
} 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();
        int res = (n/x)*t;
        if (n % x > 0){
            res += 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)*t;
        if (n % x > 0){
            res += 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)*t; res (n/x)*t (n/x) n x t if (n % x > 0){
            res += t;
        } n % x > 0 n % x n x 0 {
            res += t;
        } res += t res 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) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int res = (n/x)*t;
        if (n % x > 0){
            res += t;
        }
        System.out.println(res);
    }
} 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();
        int res = (n/x)*t;
        if (n % x > 0){
            res += t;
        }
        System.out.println(res);
    }
} Main
import java.util.*;

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();
        int res = (n/x)*t;
        if (n % x > 0){
            res += t;
        }
        System.out.println(res);
    }
}