import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  }
  
  
} import java.util.*; util.* java public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  }
  
  
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  } main {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int x = Integer.parseInt(sc.next()); x Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int t = Integer.parseInt(sc.next()); t Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int ans = n / x; ans n / x n x if(n%x > 0){
      ans++;
    } n%x > 0 n%x n x 0 {
      ans++;
    } ans++ ans ans = ans * t ans ans * t ans t System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc return; String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  }
  
  
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  }
  
  
} Main
import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int x = Integer.parseInt(sc.next());
    int t = Integer.parseInt(sc.next());
    
    int ans = n / x;
    if(n%x > 0){
      ans++;
    }
    ans = ans * t;

    System.out.println(ans);
   
    sc.close();
    return;
  }
  
  
}
