import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	}

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

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	}

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

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	} main {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String[] tmp = sc.nextLine().split(" "); tmp sc.nextLine().split(" ") sc.nextLine().split sc.nextLine() sc.nextLine sc " " int n = Integer.parseInt(tmp[0]); n Integer.parseInt(tmp[0]) Integer.parseInt Integer tmp[0] tmp 0 double x = Integer.parseInt(tmp[1]); x Integer.parseInt(tmp[1]) Integer.parseInt Integer tmp[1] tmp 1 int t = Integer.parseInt(tmp[2]); t Integer.parseInt(tmp[2]) Integer.parseInt Integer tmp[2] tmp 2 n = (int)(Math.ceil(n / x)) * t n (int)(Math.ceil(n / x)) * t (int)(Math.ceil(n / x)) Math.ceil Math n / x n x t System.out.println(n) System.out.println System.out System System.out n String[] args args public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	}

} public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] tmp = sc.nextLine().split(" ");
		int n = Integer.parseInt(tmp[0]);
		double x = Integer.parseInt(tmp[1]);
		int t = Integer.parseInt(tmp[2]);

		n = (int)(Math.ceil(n / x)) * t;
		System.out.println(n);

	}

}
