import java.util.*;
//import java.util.stream.Collectors;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	}
} import java.util.*; util.* java public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	} main {
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int x = Integer.parseInt(sc.next()); x Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int t = Integer.parseInt(sc.next()); t Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc long time = 0; time 0 while(n > 0){
			n -= x;
			time += t;
		} n > 0 n 0 {
			n -= x;
			time += t;
		} n -= x n x time += t time t System.out.println(time) System.out.println System.out System System.out time String[] args args public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	}
} public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	}
} Main
import java.util.*;
//import java.util.stream.Collectors;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		int n = Integer.parseInt(sc.next());
		int x = Integer.parseInt(sc.next());
		int t = Integer.parseInt(sc.next());
		long time = 0;
		while(n > 0){
			n -= x;
			time += t;
		}
		System.out.println(time);
	}
}
