import java.util.*;

class Main{

  public static void main(String args[]){

    Scanner s=new Scanner(System.in);
    double N=s.nextInt();
    double X=s.nextInt();
    int T=s.nextInt();
    System.out.println((int)(Math.ceil(N/X)*T));
    
  }  
} import java.util.*; util.* java class Main{

  public static void main(String args[]){

    Scanner s=new Scanner(System.in);
    double N=s.nextInt();
    double X=s.nextInt();
    int T=s.nextInt();
    System.out.println((int)(Math.ceil(N/X)*T));
    
  }  
} Main public static void main(String args[]){

    Scanner s=new Scanner(System.in);
    double N=s.nextInt();
    double X=s.nextInt();
    int T=s.nextInt();
    System.out.println((int)(Math.ceil(N/X)*T));
    
  } main {

    Scanner s=new Scanner(System.in);
    double N=s.nextInt();
    double X=s.nextInt();
    int T=s.nextInt();
    System.out.println((int)(Math.ceil(N/X)*T));
    
  } Scanner s=new Scanner(System.in); s new Scanner(System.in) double N=s.nextInt(); N s.nextInt() s.nextInt s double X=s.nextInt(); X s.nextInt() s.nextInt s int T=s.nextInt(); T s.nextInt() s.nextInt s System.out.println((int)(Math.ceil(N/X)*T)) System.out.println System.out System System.out (int)(Math.ceil(N/X)*T) Math.ceil(N/X) Math.ceil Math N/X N X T String args[] args
import java.util.*;

class Main{

  public static void main(String args[]){

    Scanner s=new Scanner(System.in);
    double N=s.nextInt();
    double X=s.nextInt();
    int T=s.nextInt();
    System.out.println((int)(Math.ceil(N/X)*T));
    
  }  
}