import java.util.Scanner;

public class Main {

	public static void main(final String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	}

	public static <T> void prtln(T t) { System.out.println(t); }
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(final String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	}

	public static <T> void prtln(T t) { System.out.println(t); }
} Main public static void main(final String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	} 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 sc.close() sc.close sc if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		} n < x n x {
			prtln(t);
		} prtln(t) prtln t {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		} prtln((int)(((double)n / (double)x) + 0.5) * t) prtln (int)(((double)n / (double)x) + 0.5) * t (int)(((double)n / (double)x) + 0.5) ((double)n / (double)x) (double)n (double)x 0.5 t final String[] args args public static <T> void prtln(T t) { System.out.println(t); } prtln { System.out.println(t); } System.out.println(t) System.out.println System.out System System.out t T t t public class Main {

	public static void main(final String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	}

	public static <T> void prtln(T t) { System.out.println(t); }
} public class Main {

	public static void main(final String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	}

	public static <T> void prtln(T t) { System.out.println(t); }
} Main
import java.util.Scanner;

public class Main {

	public static void main(final String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();
		sc.close();
		if(n < x) {
			prtln(t);
		} else {
			prtln((int)(((double)n / (double)x) + 0.5) * t);
		}
	}

	public static <T> void prtln(T t) { System.out.println(t); }
}
