
/*
 *   
 *   Date: 07 September 2019
 *   Time: 01:03:00
*/
import java.io.*; 
import java.util.*;


   
 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();
        long a=(long)Math.ceil((double)n/x);
        long b=a*t;
        System.out.println(b);
     
        
       

       
    } 
} 
 
 
  import java.io.*; io.* java import java.util.*; util.* java 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();
        long a=(long)Math.ceil((double)n/x);
        long b=a*t;
        System.out.println(b);
     
        
       

       
    } 
} 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();
        long a=(long)Math.ceil((double)n/x);
        long b=a*t;
        System.out.println(b);
     
        
       

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

       
    } 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 long a=(long)Math.ceil((double)n/x); a (long)Math.ceil((double)n/x) Math.ceil Math (double)n/x (double)n x long b=a*t; b a*t a t System.out.println(b) System.out.println System.out System System.out b String[] args args

/*
 *   
 *   Date: 07 September 2019
 *   Time: 01:03:00
*/
import java.io.*; 
import java.util.*;


   
 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();
        long a=(long)Math.ceil((double)n/x);
        long b=a*t;
        System.out.println(b);
     
        
       

       
    } 
} 
 
 
 
