import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	} main {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	} Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in))); in new Scanner(new BufferedReader(new InputStreamReader(System.in))) int n = in.nextInt(); n in.nextInt() in.nextInt in int x = in.nextInt(); x in.nextInt() in.nextInt in int t = in.nextInt(); t in.nextInt() in.nextInt in int ans = n / x; ans n / x n x if (n % x != 0)
			ans++; n % x != 0 n % x n x 0 ans++ ans ans *= t ans 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 in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	}
} Main
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int ans = n / x;
		if (n % x != 0)
			ans++;
		ans *= t;
		System.out.println(ans);
	}
}
