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();
    int u=0,t1=0;
    while(u<n){
      t1=t1+t;
      u=u+x;
    }
    System.out.println(t1);
  }} 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();
    int u=0,t1=0;
    while(u<n){
      t1=t1+t;
      u=u+x;
    }
    System.out.println(t1);
  }} 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 u=0,t1=0;
    while(u<n){
      t1=t1+t;
      u=u+x;
    }
    System.out.println(t1);
  } main {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    int u=0,t1=0;
    while(u<n){
      t1=t1+t;
      u=u+x;
    }
    System.out.println(t1);
  } 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 u=0 u 0 t1=0; t1 0 while(u<n){
      t1=t1+t;
      u=u+x;
    } u<n u n {
      t1=t1+t;
      u=u+x;
    } t1=t1+t t1 t1+t t1 t u=u+x u u+x u x System.out.println(t1) System.out.println System.out System System.out t1 String args[] args
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();
    int u=0,t1=0;
    while(u<n){
      t1=t1+t;
      u=u+x;
    }
    System.out.println(t1);
  }}