import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  }
} import java.util.ArrayList; ArrayList java.util import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner 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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  }
} 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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  } main {

    Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();

    int times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  } 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 times = n/x; times n/x n x if(n % x != 0){
      times++;
    } n % x != 0 n % x n x 0 {
      times++;
    } times++ times System.out.println(times * t) System.out.println System.out System System.out times * t times t return; 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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  }
} 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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  }
} Main
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  }
}