import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.HashSet;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N=sc.nextInt();
    int X=sc.nextInt();
    int T=sc.nextInt();


if(N%X==0){
    System.out.println(T*((N-N%X)/X));

}else{
  System.out.println(T*((N-N%X)/X+1));

}
}
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.util.stream.Collectors; Collectors java.util.stream import java.util.HashSet; HashSet java.util class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N=sc.nextInt();
    int X=sc.nextInt();
    int T=sc.nextInt();


if(N%X==0){
    System.out.println(T*((N-N%X)/X));

}else{
  System.out.println(T*((N-N%X)/X+1));

}
}
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N=sc.nextInt();
    int X=sc.nextInt();
    int T=sc.nextInt();


if(N%X==0){
    System.out.println(T*((N-N%X)/X));

}else{
  System.out.println(T*((N-N%X)/X+1));

}
} main {
    Scanner sc = new Scanner(System.in);
    int N=sc.nextInt();
    int X=sc.nextInt();
    int T=sc.nextInt();


if(N%X==0){
    System.out.println(T*((N-N%X)/X));

}else{
  System.out.println(T*((N-N%X)/X+1));

}
} 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 if(N%X==0){
    System.out.println(T*((N-N%X)/X));

}else{
  System.out.println(T*((N-N%X)/X+1));

} N%X==0 N%X N X 0 {
    System.out.println(T*((N-N%X)/X));

} System.out.println(T*((N-N%X)/X)) System.out.println System.out System System.out T*((N-N%X)/X) T ((N-N%X)/X) (N-N%X) N N%X N X X {
  System.out.println(T*((N-N%X)/X+1));

} System.out.println(T*((N-N%X)/X+1)) System.out.println System.out System System.out T*((N-N%X)/X+1) T ((N-N%X)/X+1) (N-N%X)/X (N-N%X) N N%X N X X 1 String[] args args
import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.HashSet;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N=sc.nextInt();
    int X=sc.nextInt();
    int T=sc.nextInt();


if(N%X==0){
    System.out.println(T*((N-N%X)/X));

}else{
  System.out.println(T*((N-N%X)/X+1));

}
}
}
