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 d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*t);
  }
} 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 d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*t);
  }
} 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 d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*t);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    int d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*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 int d = n/x; d n/x n x if(n%x!=0){
      d=d+1;
    } n%x!=0 n%x n x 0 {
      d=d+1;
    } d=d+1 d d+1 d 1 System.out.println(d*t) System.out.println System.out System System.out d*t d t 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 d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*t);
  }
} 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 d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*t);
  }
} 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 d = n/x;
    if(n%x!=0){
      d=d+1;
    }
    System.out.println(d*t);
  }
}