import java.util.*;

public 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 cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  }
} import java.util.*; util.* java public 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 cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  }
} 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 cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  } main {
  	Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  } 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 cnt = n/x; cnt n/x n x cnt *= t cnt t if(n%x != 0)
      cnt += t; n%x != 0 n%x n x 0 cnt += t cnt t System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public 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 cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  }
} public 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 cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  }
} Main
import java.util.*;

public 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 cnt = n/x;
    cnt *= t;
    if(n%x != 0)
      cnt += t;
    
    System.out.println(cnt);
  }
}