import java.util.*;
public class Main{
  public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  }
} import java.util.*; util.* java public class Main{
  public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  }
} Main public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  } main {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  } 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 a=0; a 0 while(n>0)
    {
       a+=t;
       n-=x;
    } n>0 n 0 {
       a+=t;
       n-=x;
    } a+=t a t n-=x n x System.out.println(a) System.out.println System.out System System.out a String arg[] arg public class Main{
  public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  }
} public class Main{
  public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  }
} Main
import java.util.*;
public class Main{
  public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    System.out.println(a);
    
  }
}