import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double N = sc.nextDouble();
		double X = sc.nextDouble();
		int T = sc.nextInt();
		sc.close();
		double ans = N / X;
		System.out.println((int)(Math.ceil(ans)*T));
	}
}
 import java.util.*; util.* java class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double N = sc.nextDouble();
		double X = sc.nextDouble();
		int T = sc.nextInt();
		sc.close();
		double ans = N / X;
		System.out.println((int)(Math.ceil(ans)*T));
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double N = sc.nextDouble();
		double X = sc.nextDouble();
		int T = sc.nextInt();
		sc.close();
		double ans = N / X;
		System.out.println((int)(Math.ceil(ans)*T));
	} main {
		Scanner sc = new Scanner(System.in);
		double N = sc.nextDouble();
		double X = sc.nextDouble();
		int T = sc.nextInt();
		sc.close();
		double ans = N / X;
		System.out.println((int)(Math.ceil(ans)*T));
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double N = sc.nextDouble(); N sc.nextDouble() sc.nextDouble sc double X = sc.nextDouble(); X sc.nextDouble() sc.nextDouble sc int T = sc.nextInt(); T sc.nextInt() sc.nextInt sc sc.close() sc.close sc double ans = N / X; ans N / X N X System.out.println((int)(Math.ceil(ans)*T)) System.out.println System.out System System.out (int)(Math.ceil(ans)*T) Math.ceil(ans) Math.ceil Math ans T String[] args args
import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double N = sc.nextDouble();
		double X = sc.nextDouble();
		int T = sc.nextInt();
		sc.close();
		double ans = N / X;
		System.out.println((int)(Math.ceil(ans)*T));
	}
}

