import java.util.*;
class Main
{
  public static void main(String args[])
  {
    int n,x,t,k;
    Scanner sc= new Scanner(System.in);
    n=sc.nextInt();
    x=sc.nextInt();
    t=sc.nextInt();
    k=n/x;
    if(n%x>0)
      k+=1;
    System.out.println(k*t);
  }
} import java.util.*; util.* java class Main
{
  public static void main(String args[])
  {
    int n,x,t,k;
    Scanner sc= new Scanner(System.in);
    n=sc.nextInt();
    x=sc.nextInt();
    t=sc.nextInt();
    k=n/x;
    if(n%x>0)
      k+=1;
    System.out.println(k*t);
  }
} Main public static void main(String args[])
  {
    int n,x,t,k;
    Scanner sc= new Scanner(System.in);
    n=sc.nextInt();
    x=sc.nextInt();
    t=sc.nextInt();
    k=n/x;
    if(n%x>0)
      k+=1;
    System.out.println(k*t);
  } main {
    int n,x,t,k;
    Scanner sc= new Scanner(System.in);
    n=sc.nextInt();
    x=sc.nextInt();
    t=sc.nextInt();
    k=n/x;
    if(n%x>0)
      k+=1;
    System.out.println(k*t);
  } int n n x x t t k; k Scanner sc= new Scanner(System.in); sc new Scanner(System.in) 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 k=n/x k n/x n x if(n%x>0)
      k+=1; n%x>0 n%x n x 0 k+=1 k 1 System.out.println(k*t) System.out.println System.out System System.out k*t k t String args[] args
import java.util.*;
class Main
{
  public static void main(String args[])
  {
    int n,x,t,k;
    Scanner sc= new Scanner(System.in);
    n=sc.nextInt();
    x=sc.nextInt();
    t=sc.nextInt();
    k=n/x;
    if(n%x>0)
      k+=1;
    System.out.println(k*t);
  }
}