import java.util.*;
import java.io.*;
class Main{
	public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int time = 0;

		while(n!=0){
			n = Math.max(n-x, 0);
			time += t;
		}

		out.println(time);
	}
} import java.util.*; util.* java import java.io.*; io.* java class Main{
	public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int time = 0;

		while(n!=0){
			n = Math.max(n-x, 0);
			time += t;
		}

		out.println(time);
	}
} Main public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int time = 0;

		while(n!=0){
			n = Math.max(n-x, 0);
			time += t;
		}

		out.println(time);
	} main {
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int time = 0;

		while(n!=0){
			n = Math.max(n-x, 0);
			time += t;
		}

		out.println(time);
	} Scanner in=new Scanner(System.in); in new Scanner(System.in) PrintWriter out = new PrintWriter(System.out, true); out new PrintWriter(System.out, true) 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 int time = 0; time 0 while(n!=0){
			n = Math.max(n-x, 0);
			time += t;
		} n!=0 n 0 {
			n = Math.max(n-x, 0);
			time += t;
		} n = Math.max(n-x, 0) n Math.max(n-x, 0) Math.max Math n-x n x 0 time += t time t out.println(time) out.println out time String[]args args
import java.util.*;
import java.io.*;
class Main{
	public static void main(String[]args){
		Scanner in=new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out, true);
		int n = in.nextInt();
		int x = in.nextInt();
		int t = in.nextInt();
		int time = 0;

		while(n!=0){
			n = Math.max(n-x, 0);
			time += t;
		}

		out.println(time);
	}
}
