import java.util.*;

class Main{
 public static void main(String[] args){
  Scanner scn = new Scanner(System.in);
   long n = scn.nextLong();
   long x = scn.nextLong();
   long t = scn.nextLong();
   
   
   System.out.println((n+x-1)/x*t);
 }
  
} import java.util.*; util.* java class Main{
 public static void main(String[] args){
  Scanner scn = new Scanner(System.in);
   long n = scn.nextLong();
   long x = scn.nextLong();
   long t = scn.nextLong();
   
   
   System.out.println((n+x-1)/x*t);
 }
  
} Main public static void main(String[] args){
  Scanner scn = new Scanner(System.in);
   long n = scn.nextLong();
   long x = scn.nextLong();
   long t = scn.nextLong();
   
   
   System.out.println((n+x-1)/x*t);
 } main {
  Scanner scn = new Scanner(System.in);
   long n = scn.nextLong();
   long x = scn.nextLong();
   long t = scn.nextLong();
   
   
   System.out.println((n+x-1)/x*t);
 } Scanner scn = new Scanner(System.in); scn new Scanner(System.in) long n = scn.nextLong(); n scn.nextLong() scn.nextLong scn long x = scn.nextLong(); x scn.nextLong() scn.nextLong scn long t = scn.nextLong(); t scn.nextLong() scn.nextLong scn System.out.println((n+x-1)/x*t) System.out.println System.out System System.out (n+x-1)/x*t (n+x-1)/x (n+x-1) n+x n x 1 x t String[] args args
import java.util.*;

class Main{
 public static void main(String[] args){
  Scanner scn = new Scanner(System.in);
   long n = scn.nextLong();
   long x = scn.nextLong();
   long t = scn.nextLong();
   
   
   System.out.println((n+x-1)/x*t);
 }
  
}
