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();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	}

} 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();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	}

} 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();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	} main {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	} 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){
		System.out.println(T);
		return;
       } N<=X N X {
		System.out.println(T);
		return;
       } System.out.println(T) System.out.println System.out System System.out T return; int times = (int) Math.floor(N/X); times (int) Math.floor(N/X) Math.floor Math N/X N X if(N%X!=0){
		times++;
       } N%X!=0 N%X N X 0 {
		times++;
       } times++ times System.out.println(T*times) System.out.println System.out System System.out T*times T times return; 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();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	}

} 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();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	}

} 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();
      
      if(N<=X){
		System.out.println(T);
		return;
       }
      
		int times = (int) Math.floor(N/X);
      
       if(N%X!=0){
		times++;
       }
		System.out.println(T*times);
		return;
	}

}
