import java.util.Scanner;

public class Main {

	public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	}
} Main public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	} main {

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	} 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 int i=0; i 0 int t=0; t 0 for(i=0;i<N;i=i+X) {
		t=t+T;
	} i=0; i=0 i 0 i<N i N i=i+X i=i+X i i+X i X {
		t=t+T;
	} {
		t=t+T;
	} t=t+T t t+T t T System.out.println(t) System.out.println System.out System System.out t String[] aggs aggs public class Main {

	public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	}
} public class Main {

	public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] aggs){

	Scanner stdIn = new Scanner(System.in);
	int N = stdIn.nextInt();
	int X = stdIn.nextInt();
	int T = stdIn.nextInt();

	int i=0;
	int t=0;

	for(i=0;i<N;i=i+X) {
		t=t+T;
	}

	System.out.println(t);

	}
}
