import java.util.*;

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

public class Main {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    long n = in.nextLong();
    long x = in.nextLong();
    long t = in.nextLong();
    long temp = (long) Math.ceil((double) n/x);
    System.out.println(temp*t);
    in.close();
  }
}
