import java.util.*;
public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        }
        public static void main(String[]args){
            new Main().solve();
        }
    } import java.util.*; util.* java public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        }
        public static void main(String[]args){
            new Main().solve();
        }
    } Main public void solve() {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        } solve {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int X = scan.nextInt(); X scan.nextInt() scan.nextInt scan int T = scan.nextInt(); T scan.nextInt() scan.nextInt scan int a; a if(N%X == 0) a=N/X;
       else a=N/X+1; N%X == 0 N%X N X 0 a=N/X a N/X N X a=N/X+1 a N/X+1 N/X N X 1 System.out.println(a*T) System.out.println System.out System System.out a*T a T public static void main(String[]args){
            new Main().solve();
        } main {
            new Main().solve();
        } new Main().solve() new Main().solve new Main() String[]args args public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        }
        public static void main(String[]args){
            new Main().solve();
        }
    } public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        }
        public static void main(String[]args){
            new Main().solve();
        }
    } Main
import java.util.*;
public class Main {
    public void solve() {
        Scanner scan = new Scanner(System.in);
       int N = scan.nextInt();
       int X = scan.nextInt();
       int T = scan.nextInt();
       int a;
       if(N%X == 0) a=N/X;
       else a=N/X+1;
       System.out.println(a*T);
        }
        public static void main(String[]args){
            new Main().solve();
        }
    }