import java.util.*;
class Main{
	public static void main(String[] args){
	  Scanner scan = new Scanner(System.in);
	  int N = scan.nextInt();
      int X = scan.nextInt();
      int T = scan.nextInt();
      int time = 0;
      if(N%X == 0) time = (N/X) * T;
      else time = ((N/X)+1)*T;
      System.out.println(time);
	}
} import java.util.*; util.* java class Main{
	public static void main(String[] args){
	  Scanner scan = new Scanner(System.in);
	  int N = scan.nextInt();
      int X = scan.nextInt();
      int T = scan.nextInt();
      int time = 0;
      if(N%X == 0) time = (N/X) * T;
      else time = ((N/X)+1)*T;
      System.out.println(time);
	}
} Main public static void main(String[] args){
	  Scanner scan = new Scanner(System.in);
	  int N = scan.nextInt();
      int X = scan.nextInt();
      int T = scan.nextInt();
      int time = 0;
      if(N%X == 0) time = (N/X) * T;
      else time = ((N/X)+1)*T;
      System.out.println(time);
	} main {
	  Scanner scan = new Scanner(System.in);
	  int N = scan.nextInt();
      int X = scan.nextInt();
      int T = scan.nextInt();
      int time = 0;
      if(N%X == 0) time = (N/X) * T;
      else time = ((N/X)+1)*T;
      System.out.println(time);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int X = scan.nextInt(); X scan.nextInt() scan.nextInt scan int T = scan.nextInt(); T scan.nextInt() scan.nextInt scan int time = 0; time 0 if(N%X == 0) time = (N/X) * T;
      else time = ((N/X)+1)*T; N%X == 0 N%X N X 0 time = (N/X) * T time (N/X) * T (N/X) N X T time = ((N/X)+1)*T time ((N/X)+1)*T ((N/X)+1) (N/X) N X 1 T System.out.println(time) System.out.println System.out System System.out time String[] args args
import java.util.*;
class Main{
	public static void main(String[] args){
	  Scanner scan = new Scanner(System.in);
	  int N = scan.nextInt();
      int X = scan.nextInt();
      int T = scan.nextInt();
      int time = 0;
      if(N%X == 0) time = (N/X) * T;
      else time = ((N/X)+1)*T;
      System.out.println(time);
	}
}