import java.util.Scanner;

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 ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  }
} import java.util.Scanner; Scanner 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 ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  }
} 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 ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    int ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  } 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 ans = 0; ans 0 ans += n / x ans n / x n x if (n % x != 0) {
      ans++;
    } n % x != 0 n % x n x 0 {
      ans++;
    } ans++ ans System.out.println(ans * t) System.out.println System.out System System.out ans * t ans t sc.close() sc.close sc 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 ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  }
} 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 ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  }
} Main
import java.util.Scanner;

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 ans = 0;
    ans += n / x;
    if (n % x != 0) {
      ans++;
    }
    System.out.println(ans * t);
    sc.close();
  }
}
