import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		if(n%x == 0) {
			System.out.println((n/x)*t);
		}else {
			System.out.println(((n/x)+1)*t);
		}
		
		
	}
	
	
	public static int gcd(int x,int y) {
		if(x%y == 0) {
			return y;
		}else {
			return gcd(y,x%y);
		}
	}
}
 


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

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

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

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		if(n%x == 0) {
			System.out.println((n/x)*t);
		}else {
			System.out.println(((n/x)+1)*t);
		}
		
		
	}
	
	
	public static int gcd(int x,int y) {
		if(x%y == 0) {
			return y;
		}else {
			return gcd(y,x%y);
		}
	}
} Main
import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		if(n%x == 0) {
			System.out.println((n/x)*t);
		}else {
			System.out.println(((n/x)+1)*t);
		}
		
		
	}
	
	
	public static int gcd(int x,int y) {
		if(x%y == 0) {
			return y;
		}else {
			return gcd(y,x%y);
		}
	}
}
 



