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

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	}

}
/*class Reader{
	BufferedReader reader;
	Reader(){
		reader=new BufferedReader(new InputStreamReader(System.in));
	}
	int nextInt() throws IOException{
		String in=reader.readLine().trim();
		return Integer.parseInt(in);
	}
	long nextLong() throws IOException{
		String in=reader.readLine().trim();
		return Long.parseLong(in);
	}
	String next() throws IOException{
		return reader.readLine().trim();
	}
	String[] stringArray() throws IOException{
		return reader.readLine().trim().split("\\s+");
	}
	int[] intArray() throws IOException{
		String[] inp=this.stringArray();
		int[] arr=new int[inp.length];
		int i=0;
		for(String s:inp) {
			arr[i++]=Integer.parseInt(s);
		}
		return arr;
	}
}*/

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

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	}

} Main public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	} main {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int t=1; t 1 while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		} t-->0 t-- t 0 {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		} 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 val=n/x+(n%x==0? 0:1); val n/x+(n%x==0? 0:1) n/x n x (n%x==0? 0:1) n%x==0 n%x n x 0 0 1 System.out.println(val*T) System.out.println System.out System System.out val*T val T String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	}

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

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	}

}
/*class Reader{
	BufferedReader reader;
	Reader(){
		reader=new BufferedReader(new InputStreamReader(System.in));
	}
	int nextInt() throws IOException{
		String in=reader.readLine().trim();
		return Integer.parseInt(in);
	}
	long nextLong() throws IOException{
		String in=reader.readLine().trim();
		return Long.parseLong(in);
	}
	String next() throws IOException{
		return reader.readLine().trim();
	}
	String[] stringArray() throws IOException{
		return reader.readLine().trim().split("\\s+");
	}
	int[] intArray() throws IOException{
		String[] inp=this.stringArray();
		int[] arr=new int[inp.length];
		int i=0;
		for(String s:inp) {
			arr[i++]=Integer.parseInt(s);
		}
		return arr;
	}
}*/


