import java.util.Scanner;

public class Main{
public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
}
} import java.util.Scanner; Scanner java.util public class Main{
public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
}
} Main public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
} main {
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
} Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn int x = stdIn.nextInt(); x stdIn.nextInt() stdIn.nextInt stdIn int t = stdIn.nextInt(); t stdIn.nextInt() stdIn.nextInt stdIn if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));} n%x == 0 n%x n x 0 {System.out.println(t*(n/x));} System.out.println(t*(n/x)) System.out.println System.out System System.out t*(n/x) t (n/x) n x {System.out.println(t*(n/x + 1));} System.out.println(t*(n/x + 1)) System.out.println System.out System System.out t*(n/x + 1) t (n/x + 1) n/x n x 1 String[]  args args public class Main{
public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
}
} public class Main{
public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
}
} Main
import java.util.Scanner;

public class Main{
public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
}
}