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();
      
      int c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(a);
      
    }
} 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();
      
      int c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(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 c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(a);
      
    } main {
    Scanner sc = new Scanner(System.in);
      int n= sc.nextInt();
      int x =sc.nextInt();
      int t =sc.nextInt();
      
      int c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(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 c; c int a; a c = (n+x-1)/x c (n+x-1)/x (n+x-1) n+x n x 1 x a = c*t a c*t c t System.out.println(a) System.out.println System.out System System.out 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 c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(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 c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(a);
      
    }
} 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();
      
      int c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(a);
      
    }
}