import java.util.*;

public class Main {
	public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      }
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      }
} Main public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      } main {
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      } Scanner sc = null; sc null 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 sc.close() sc.close sc int ans = 0; ans 0 for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        } int i = 0; int i = 0; i 0 i < 1000 i 1000 i++ i++ i {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        } {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        } ans += t ans t n -= x n x if (n <= 0) {
                break;
            } n <= 0 n 0 {
                break;
            } break; System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
	public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      }
} public class Main {
	public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      }
} Main
import java.util.*;

public class Main {
	public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      }
}