import java.util.Scanner;
import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	}

} import java.util.Scanner; Scanner java.util import java.util.*; util.* java public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	}

} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	} main {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = Integer.parseInt(scan.next()); N Integer.parseInt(scan.next()) Integer.parseInt Integer scan.next() scan.next scan int X = Integer.parseInt(scan.next()); X Integer.parseInt(scan.next()) Integer.parseInt Integer scan.next() scan.next scan int T = Integer.parseInt(scan.next()); T Integer.parseInt(scan.next()) Integer.parseInt Integer scan.next() scan.next scan int ans = 0; ans 0 while (N > 0) {
			ans+=T;
			N-=X;
		} N > 0 N 0 {
			ans+=T;
			N-=X;
		} ans+=T ans T N-=X N X System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	}

} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	}

} Main
import java.util.Scanner;
import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.next());
		int X = Integer.parseInt(scan.next());
		int T = Integer.parseInt(scan.next());
		int ans = 0;

		while (N > 0) {
			ans+=T;
			N-=X;
		}
		System.out.println(ans);
	}

}
