import java.util.Scanner;

public class Main{
  public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  }
}
 import java.util.Scanner; Scanner java.util public class Main{
  public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  }
} Main public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  } main {
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) double n = scanner.nextInt(); n scanner.nextInt() scanner.nextInt scanner double x = scanner.nextInt(); x scanner.nextInt() scanner.nextInt scanner double t = scanner.nextInt(); t scanner.nextInt() scanner.nextInt scanner int kaisu = (int)Math.ceil(n/x); kaisu (int)Math.ceil(n/x) Math.ceil Math n/x n x System.out.println((int)t*kaisu) System.out.println System.out System System.out (int)t*kaisu (int)t kaisu String args[] args public class Main{
  public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  }
} public class Main{
  public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  }
} Main
import java.util.Scanner;

public class Main{
  public static void main(String args[]){
    Scanner scanner = new Scanner(System.in);
    double n = scanner.nextInt();
    double x = scanner.nextInt();
    double t = scanner.nextInt();

    int kaisu = (int)Math.ceil(n/x); 
    //System.out.println(kaisu);
    System.out.println((int)t*kaisu);
    
  }
}

