import java.util.*;

public class  Main{
    static Scanner s = new Scanner(System.in);

    public static void main(String[] args){
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    }
} import java.util.*; util.* java public class  Main{
    static Scanner s = new Scanner(System.in);

    public static void main(String[] args){
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    }
} Main static Scanner s = new Scanner(System.in); s new Scanner(System.in) public static void main(String[] args){
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    } main {
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    } int n = s.nextInt() n s.nextInt() s.nextInt s x = s.nextInt() x s.nextInt() s.nextInt s t = s.nextInt(); t s.nextInt() s.nextInt s int count = 0; count 0 count = n / x * t count n / x * t n / x n x t if (n % x > 0)
            count += t; n % x > 0 n % x n x 0 count += t count t System.out.println(count) System.out.println System.out System System.out count String[] args args public class  Main{
    static Scanner s = new Scanner(System.in);

    public static void main(String[] args){
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    }
} public class  Main{
    static Scanner s = new Scanner(System.in);

    public static void main(String[] args){
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    }
} Main
import java.util.*;

public class  Main{
    static Scanner s = new Scanner(System.in);

    public static void main(String[] args){
        int n = s.nextInt(), x = s.nextInt(), t = s.nextInt();
        int count = 0;
        count = n / x * t;
        if (n % x > 0)
            count += t;

        System.out.println(count);
    }
}
