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 times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    }
} 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 times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    }
} 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 times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    } 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 times; times if(n%x == 0) times = n / x;
        else times = n / x + 1; n%x == 0 n%x n x 0 times = n / x times n / x n x times = n / x + 1 times n / x + 1 n / x n x 1 System.out.println(t * times) System.out.println System.out System System.out t * times t times 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 times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    }
} 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 times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    }
} 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 times;
        if(n%x == 0) times = n / x;
        else times = n / x + 1;

        System.out.println(t * times);
    }
}
