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 n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    }
} 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 n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    }
} 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 n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    } main {

        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();


        int n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    } 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 n = N/X; n N/X N X if (N % X > 0) {
            n++;
        } N % X > 0 N % X N X 0 {
            n++;
        } n++ n int result = n * T; result n * T n T System.out.println(result) System.out.println System.out System System.out result 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 n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    }
} 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 n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    }
} 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 n = N/X;

        if (N % X > 0) {
            n++;
        }

        int result = n * T;
        System.out.println(result);


    }
}