import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	}
} import java.util.*; util.* java public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int X = sc.nextInt(); X sc.nextInt() sc.nextInt sc int T = sc.nextInt(); T sc.nextInt() sc.nextInt sc System.out.println((N+X-1)/X*T) System.out.println System.out System System.out (N+X-1)/X*T (N+X-1)/X (N+X-1) N+X N X 1 X T sc.close() sc.close sc String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	}
} Main
import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		System.out.println((N+X-1)/X*T);
		
		sc.close();
	}
}
