/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	}
} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	}
} Main public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	} main {
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	} Scanner scan=new Scanner(System.in); scan new Scanner(System.in) int n=scan.nextInt() n scan.nextInt() scan.nextInt scan x=scan.nextInt() x scan.nextInt() scan.nextInt scan t=scan.nextInt(); t scan.nextInt() scan.nextInt scan int c=x c x time=t; time t while(c<n)
	    {
	        c+=x;
	        time+=t;
	    } c<n c n {
	        c+=x;
	        time+=t;
	    } c+=x c x time+=t time t System.out.println(time) System.out.println System.out System System.out time String[] args args public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	}
} public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	}
} Main
/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner scan=new Scanner(System.in);
	    int n=scan.nextInt(),x=scan.nextInt(),t=scan.nextInt();
	    int c=x,time=t;
	    while(c<n)
	    {
	        c+=x;
	        time+=t;
	    }
	    System.out.println(time);
	}
}
