import java.util.*;
// warm-up
public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	}

	public static void main(String args[]) {
		solve();
	}

} import java.util.*; util.* java public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	}

	public static void main(String args[]) {
		solve();
	}

} Main static void solve() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	} solve {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) 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 s = ((n/x)*t) + ((n%x>0) ? t : 0); s ((n/x)*t) + ((n%x>0) ? t : 0) ((n/x)*t) (n/x) n x t ((n%x>0) ? t : 0) (n%x>0) n%x n x 0 t 0 System.out.println(s) System.out.println System.out System System.out s sc.close() sc.close sc public static void main(String args[]) {
		solve();
	} main {
		solve();
	} solve() solve String args[] args public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	}

	public static void main(String args[]) {
		solve();
	}

} public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	}

	public static void main(String args[]) {
		solve();
	}

} Main
import java.util.*;
// warm-up
public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt(), x=sc.nextInt(), t=sc.nextInt();
		int s = ((n/x)*t) + ((n%x>0) ? t : 0);
		System.out.println(s);
		sc.close();		
	}

	public static void main(String args[]) {
		solve();
	}

}
