import java.util.*;
public 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();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    }
} import java.util.*; util.* java public 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();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    }
} 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();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    } 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 times = N/X + ((N%X == 0) ? 0 : 1); times N/X + ((N%X == 0) ? 0 : 1) N/X N X ((N%X == 0) ? 0 : 1) (N%X == 0) N%X N X 0 0 1 System.out.println(times*T) System.out.println System.out System System.out times*T times T String[] args args public 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();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    }
} public 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();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    }
} Main
import java.util.*;
public 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();
        
        int times = N/X + ((N%X == 0) ? 0 : 1);
        System.out.println(times*T);
    }
}
