import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		execute20_3();
	}
	
	private static void execute20_3() {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	}
} import java.util.ArrayDeque; ArrayDeque java.util import java.util.ArrayList; ArrayList java.util import java.util.Arrays; Arrays java.util import java.util.Comparator; Comparator java.util import java.util.Deque; Deque java.util import java.util.HashMap; HashMap java.util import java.util.HashSet; HashSet java.util import java.util.List; List java.util import java.util.Map; Map java.util import java.util.Queue; Queue java.util import java.util.Scanner; Scanner java.util import java.util.Set; Set java.util public class Main {

	public static void main(String[] args) {
		execute20_3();
	}
	
	private static void execute20_3() {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	}
} Main public static void main(String[] args) {
		execute20_3();
	} main {
		execute20_3();
	} execute20_3() execute20_3 String[] args args private static void execute20_3() {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	} execute20_3 {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	} try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		} {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		} Scanner sc = new Scanner(System.in) Scanner sc = new Scanner(System.in) 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 System.out.println((n+x-1)/x*t) System.out.println System.out System System.out (n+x-1)/x*t (n+x-1)/x (n+x-1) n+x n x 1 x t public class Main {

	public static void main(String[] args) {
		execute20_3();
	}
	
	private static void execute20_3() {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	}
} public class Main {

	public static void main(String[] args) {
		execute20_3();
	}
	
	private static void execute20_3() {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	}
} Main
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		execute20_3();
	}
	
	private static void execute20_3() {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int x = sc.nextInt();
			int t = sc.nextInt();
				System.out.println((n+x-1)/x*t);
		}
	}
}