import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Vector;
import java.util.concurrent.CountDownLatch;

public class Main {
	//2-100
	public static void main(String args[]) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	}
	

} import java.util.Arrays; Arrays java.util import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util import java.util.Vector; Vector java.util import java.util.concurrent.CountDownLatch; CountDownLatch java.util.concurrent public class Main {
	//2-100
	public static void main(String args[]) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	}
	

} Main //2-100
	public static void main(String args[]) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	} main {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	} Scanner in = new Scanner(System.in); in new Scanner(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 if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		} n%x==0 n%x n x 0 {
			int total = n/x;
			System.out.println(total*t);
		} int total = n/x; total n/x n x System.out.println(total*t) System.out.println System.out System System.out total*t total t {
			int total = n/x;
			System.out.println((total+1)*t);
		} int total = n/x; total n/x n x System.out.println((total+1)*t) System.out.println System.out System System.out (total+1)*t (total+1) total 1 t String args[] args public class Main {
	//2-100
	public static void main(String args[]) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	}
	

} public class Main {
	//2-100
	public static void main(String args[]) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	}
	

} Main
import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Vector;
import java.util.concurrent.CountDownLatch;

public class Main {
	//2-100
	public static void main(String args[]) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		if (n%x==0) {
			int total = n/x;
			System.out.println(total*t);
		}else {
			int total = n/x;
			System.out.println((total+1)*t);
		}
		
		
		
	}
	

}