import java.util.Scanner;
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();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	}

} import java.util.Scanner; Scanner 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();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	}

} 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();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	} main {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		int X=sc.nextInt();
		int T=sc.nextInt();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	} 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 int a=N/X; a N/X N X if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		} N%X!=0 N%X N X 0 {
			System.out.println(T*(a+1));
		} System.out.println(T*(a+1)) System.out.println System.out System System.out T*(a+1) T (a+1) a 1 {
			System.out.println(T*a);
		} System.out.println(T*a) System.out.println System.out System System.out T*a T a 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();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	}

} 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();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	}

} Main
import java.util.Scanner;
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();
		int a=N/X;
		
		if(N%X!=0) {
			System.out.println(T*(a+1));
		}else {
			System.out.println(T*a);
		}
	}

}