import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int x = Integer.parseInt(sc.next()); x Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int t = Integer.parseInt(sc.next()); t Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int answer = 0; answer 0 int takoyaki = 0; takoyaki 0 while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        } takoyaki < n takoyaki n {
            takoyaki += x;
            answer += t;
        } takoyaki += x takoyaki x answer += t answer t System.out.println(answer) System.out.println System.out System System.out answer sc.close() sc.close sc String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int x = Integer.parseInt(sc.next());
        int t = Integer.parseInt(sc.next());
        int answer = 0;
        int takoyaki = 0;
        while (takoyaki < n) {
            takoyaki += x;
            answer += t;
        }
        System.out.println(answer);
        sc.close();
    }
}