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

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();

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