import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner scn  = new Scanner(System.in);
		int n = scn.nextInt();
		int x = scn.nextInt();
		int t = scn.nextInt();
		int fac = n/x;
		if(n%x!=0)
			fac++;
		System.out.println(fac*t);

	}



} import java.util.*; util.* java public class Main {
	public static void main(String[] args) {
		Scanner scn  = new Scanner(System.in);
		int n = scn.nextInt();
		int x = scn.nextInt();
		int t = scn.nextInt();
		int fac = n/x;
		if(n%x!=0)
			fac++;
		System.out.println(fac*t);

	}



} Main public static void main(String[] args) {
		Scanner scn  = new Scanner(System.in);
		int n = scn.nextInt();
		int x = scn.nextInt();
		int t = scn.nextInt();
		int fac = n/x;
		if(n%x!=0)
			fac++;
		System.out.println(fac*t);

	} main {
		Scanner scn  = new Scanner(System.in);
		int n = scn.nextInt();
		int x = scn.nextInt();
		int t = scn.nextInt();
		int fac = n/x;
		if(n%x!=0)
			fac++;
		System.out.println(fac*t);

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

	}



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

	}



} Main
import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner scn  = new Scanner(System.in);
		int n = scn.nextInt();
		int x = scn.nextInt();
		int t = scn.nextInt();
		int fac = n/x;
		if(n%x!=0)
			fac++;
		System.out.println(fac*t);

	}



}
