// 提出時に消す
// package app;

import java.util.Scanner;

// 提出時にMainに変更する
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    } 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 kaisu = n / x; kaisu n / x n x if (n % x > 0) {
            kaisu++;
        } n % x > 0 n % x n x 0 {
            kaisu++;
        } kaisu++ kaisu System.out.println(t * kaisu) System.out.println System.out System System.out t * kaisu t kaisu sc.close() sc.close sc String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    }
} Main
// 提出時に消す
// package app;

import java.util.Scanner;

// 提出時にMainに変更する
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

        int kaisu = n / x;
        if (n % x > 0) {
            kaisu++;
        }

        System.out.println(t * kaisu);

        sc.close();
    }
}