import java.util.Scanner;

public class Main {
	public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    }
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    }
} Main public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    } main {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    } Scanner sn = new Scanner(System.in); sn new Scanner(System.in) int n = sn.nextInt(); n sn.nextInt() sn.nextInt sn int x = sn.nextInt(); x sn.nextInt() sn.nextInt sn int t = sn.nextInt(); t sn.nextInt() sn.nextInt sn int res = n / x; res n / x n x int mod = n % x; mod n % x n x if(mod != 0) {
        	res++;
        } mod != 0 mod 0 {
        	res++;
        } res++ res res = res * t res res * t res t System.out.println(res) System.out.println System.out System System.out res String [] args args public class Main {
	public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    }
} public class Main {
	public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    }
} Main
import java.util.Scanner;

public class Main {
	public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    }
}