import java.util.Scanner;
public class Main {
    public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    }
} Main public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    } main {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    } Scanner s=new Scanner(System.in); s new Scanner(System.in) int n=s.nextInt(); n s.nextInt() s.nextInt s int x=s.nextInt(); x s.nextInt() s.nextInt s int t=s.nextInt(); t s.nextInt() s.nextInt s int ans=(int)Math.ceil((double)n/x); ans (int)Math.ceil((double)n/x) Math.ceil Math (double)n/x (double)n x ans*=t ans t System.out.print(ans) System.out.print System.out System System.out ans String args[] args public class Main {
    public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    }
} public class Main {
    public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    }
} Main
import java.util.Scanner;
public class Main {
    public static void main(String args[]) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int x=s.nextInt();
        int t=s.nextInt();
        int ans=(int)Math.ceil((double)n/x);
        ans*=t;
        System.out.print(ans);

    }
}