import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	}

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

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	}

} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	} main {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan int x = scan.nextInt(); x scan.nextInt() scan.nextInt scan int t = scan.nextInt(); t scan.nextInt() scan.nextInt scan int ans = 0; ans 0 int a = n/x; a n/x n x int b = n%x; b n%x n x if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		} b == 0 b 0 {
			System.out.println(a*t);
		} System.out.println(a*t) System.out.println System.out System System.out a*t a t {
			System.out.println(a*t+t);
		} System.out.println(a*t+t) System.out.println System.out System System.out a*t+t a*t a t t String[] args args public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	}

} public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		int ans = 0;
		int a = n/x;
		int b = n%x;
		
		
		if(b == 0) {
			System.out.println(a*t);
		}
		else {
			System.out.println(a*t+t);
		}
	}

}
