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 time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	}
} 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 time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	}
} 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 time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	} main {

		Scanner sc = new Scanner(System.in);

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

		int time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	} 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 time = 0; time 0 while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		} true {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		} time += t time t n -= x n x if (n <= 0) {
				System.out.println(time);
				return;

			} n <= 0 n 0 {
				System.out.println(time);
				return;

			} System.out.println(time) System.out.println System.out System System.out time return; 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 time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	}
} 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 time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	}
} 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 time = 0;

		while (true) {
			time += t;

			n -= x;

			if (n <= 0) {
				System.out.println(time);
				return;

			}
		}

	}
}