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 time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    }
} 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 time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    }
} 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 time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        int time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    } 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 time = t; time t while(x < n){
            n -= x;
            time += t;
        } x < n x n {
            n -= x;
            time += t;
        } n -= x n x time += t time t System.out.println(time) System.out.println System.out System System.out time 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 time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    }
} 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 time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    }
} 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 time = t;
        while(x < n){
            n -= x;
            time += t;
        }
        System.out.println(time);
    }
}