import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Main
{
 public static void main(String args[])
  {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
    int a;
    if(n%x==0) a=n/x;
    else a=n/x+1;
    System.out.println(a*t);
  }
} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java class Main
{
 public static void main(String args[])
  {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
    int a;
    if(n%x==0) a=n/x;
    else a=n/x+1;
    System.out.println(a*t);
  }
} Main public static void main(String args[])
  {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
    int a;
    if(n%x==0) a=n/x;
    else a=n/x+1;
    System.out.println(a*t);
  } main {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
    int a;
    if(n%x==0) a=n/x;
    else a=n/x+1;
    System.out.println(a*t);
  } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int n=sc.nextInt() n sc.nextInt() sc.nextInt sc x=sc.nextInt() x sc.nextInt() sc.nextInt sc t=sc.nextInt(); t sc.nextInt() sc.nextInt sc int a; a if(n%x==0) a=n/x;
    else a=n/x+1; n%x==0 n%x n x 0 a=n/x a n/x n x a=n/x+1 a n/x+1 n/x n x 1 System.out.println(a*t) System.out.println System.out System System.out a*t a t String args[] args
import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Main
{
 public static void main(String args[])
  {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
    int a;
    if(n%x==0) a=n/x;
    else a=n/x+1;
    System.out.println(a*t);
  }
}
