
import java.io.IOException;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws IOException{

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	}
} import java.io.IOException; IOException java.io import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) throws IOException{

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	}
} Main public static void main(String[] args) throws IOException{

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	} main {

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	} 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 if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		} N/X == 0 N/X N X 0 {
			System.out.println(T);
		} System.out.println(T) System.out.println System.out System System.out T {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		} int i = N/X; i N/X N X if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			} N%X==0 N%X N X 0 {
				System.out.println(T*i);
			} System.out.println(T*i) System.out.println System.out System System.out T*i T i {
				System.out.println(T*i + T);
			} System.out.println(T*i + T) System.out.println System.out System System.out T*i + T T*i T i T String[] args args public class Main {

	public static void main(String[] args) throws IOException{

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	}
} public class Main {

	public static void main(String[] args) throws IOException{

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	}
} Main

import java.io.IOException;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws IOException{

		Scanner sc = new Scanner(System.in);
		int N =sc.nextInt();
		int X =sc.nextInt();
		int T =sc.nextInt();

		if(N/X == 0) {
			System.out.println(T);
		}
		else {
			int i = N/X;
			if(N%X==0) {
				System.out.println(T*i);
			}
			else {
				System.out.println(T*i + T);
			}
		}
	}
}
