import java.util.Scanner;

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();
      	sc.close();
    	
    	int total = n % x == 0 ? n / x : n / x + 1;
    	
    	System.out.println(total * t);
    	
    	
    	
    }

} import java.util.Scanner; Scanner java.util 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();
      	sc.close();
    	
    	int total = n % x == 0 ? n / x : n / x + 1;
    	
    	System.out.println(total * t);
    	
    	
    	
    }

} 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();
      	sc.close();
    	
    	int total = n % x == 0 ? n / x : n / x + 1;
    	
    	System.out.println(total * t);
    	
    	
    	
    } main {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	int x = sc.nextInt();
    	int t = sc.nextInt();
      	sc.close();
    	
    	int total = n % x == 0 ? n / x : n / x + 1;
    	
    	System.out.println(total * t);
    	
    	
    	
    } 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 sc.close() sc.close sc int total = n % x == 0 ? n / x : n / x + 1; total n % x == 0 ? n / x : n / x + 1 n % x == 0 n % x n x 0 n / x n x n / x + 1 n / x n x 1 System.out.println(total * t) System.out.println System.out System System.out total * t total t String[] args args
import java.util.Scanner;

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();
      	sc.close();
    	
    	int total = n % x == 0 ? n / x : n / x + 1;
    	
    	System.out.println(total * t);
    	
    	
    	
    }

}