import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	}

} import java.util.*; util.* java public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	} main {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String[] a = sc.nextLine().split(" "); a sc.nextLine().split(" ") sc.nextLine().split sc.nextLine() sc.nextLine sc " " int n = Integer.parseInt(a[0]); n Integer.parseInt(a[0]) Integer.parseInt Integer a[0] a 0 int x =  Integer.parseInt(a[1]) ; x Integer.parseInt(a[1]) Integer.parseInt Integer a[1] a 1 int t =  Integer.parseInt(a[2]); t Integer.parseInt(a[2]) Integer.parseInt Integer a[2] a 2 int answer = 0; answer 0 while (n > 0) {
			n -= x;
			answer += t;
		} n > 0 n 0 {
			n -= x;
			answer += t;
		} n -= x n x answer += t answer t System.out.println(answer) System.out.println System.out System System.out answer String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	}

} Main
import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] a = sc.nextLine().split(" ");
		int n = Integer.parseInt(a[0]);
		int x =  Integer.parseInt(a[1]) ;
		int t =  Integer.parseInt(a[2]);
		int answer = 0;
		while (n > 0) {
			n -= x;
			answer += t;
		}
		System.out.println(answer);
	}

}