import java.util.*;
import java.io.*;
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 calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  }
} import java.util.*; util.* java import java.io.*; io.* java 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 calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  }
} 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 calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  } main {
   Scanner sc = new Scanner(System.in);
   int n = sc.nextInt();
   int x = sc.nextInt();
   int t = sc.nextInt();

   int calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  } 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 calc = n / x; calc n / x n x if (n % x > 0) {
     calc++;
   } n % x > 0 n % x n x 0 {
     calc++;
   } calc++ calc System.out.println(calc * t) System.out.println System.out System System.out calc * t calc t 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 calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  }
} 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 calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  }
} Main
import java.util.*;
import java.io.*;
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 calc = n / x;
   if (n % x > 0) {
     calc++;
   }
   System.out.println(calc * t);
  }
}
