import java.util.*;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	}
} import java.util.*; util.* java public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	} Scanner sc = new Scanner(System.in); sc 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 int q = N / X; q N / X N X int r = N % X; r N % X N X int s; s if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		} r == 0 r 0 {
			s = q * T;
		} s = q * T s q * T q T {
			s = (q + 1) * T;
		} s = (q + 1) * T s (q + 1) * T (q + 1) q 1 T System.out.println(s) System.out.println System.out System System.out s String[] args args public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	}
} public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	}
} Main
import java.util.*;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		
		int q = N / X;
		int r = N % X;
		int s;
		if(r == 0) {
			s = q * T;
		}
		else {
			s = (q + 1) * T;
		}
		System.out.println(s);
	}
}