import java.util.*;
 
class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int max = sc.nextInt();
    int t = sc.nextInt();
    
    double num = (double)n / (double)max;
    num = Math.ceil(num);
    System.out.print((int)num * t);
  }
} import java.util.*; util.* java class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int max = sc.nextInt();
    int t = sc.nextInt();
    
    double num = (double)n / (double)max;
    num = Math.ceil(num);
    System.out.print((int)num * t);
  }
} Main public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int max = sc.nextInt();
    int t = sc.nextInt();
    
    double num = (double)n / (double)max;
    num = Math.ceil(num);
    System.out.print((int)num * t);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int max = sc.nextInt();
    int t = sc.nextInt();
    
    double num = (double)n / (double)max;
    num = Math.ceil(num);
    System.out.print((int)num * t);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int max = sc.nextInt(); max sc.nextInt() sc.nextInt sc int t = sc.nextInt(); t sc.nextInt() sc.nextInt sc double num = (double)n / (double)max; num (double)n / (double)max (double)n (double)max num = Math.ceil(num) num Math.ceil(num) Math.ceil Math num System.out.print((int)num * t) System.out.print System.out System System.out (int)num * t (int)num t 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 max = sc.nextInt();
    int t = sc.nextInt();
    
    double num = (double)n / (double)max;
    num = Math.ceil(num);
    System.out.print((int)num * t);
  }
}