import java.util.Scanner;
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 ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	}

} import java.util.Scanner; Scanner 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 ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	}

} 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 ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	} main {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		int ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	} 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 ans = 0; ans 0 while(n > 0) {
			n -= x;
			ans++;
		} n > 0 n 0 {
			n -= x;
			ans++;
		} n -= x n x ans++ ans System.out.println(ans*t) System.out.println System.out System System.out ans*t ans t 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 ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	}

} 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 ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	}

} Main
import java.util.Scanner;
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 ans = 0;

		while(n > 0) {
			n -= x;
			ans++;
		}
		System.out.println(ans*t);

	}

}