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();
		System.out.println((N / X + Math.min(1, N % X)) * T);
	}
} 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();
		System.out.println((N / X + Math.min(1, N % X)) * T);
	}
} 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();
		System.out.println((N / X + Math.min(1, N % X)) * T);
	} main {
		Scanner stdIn = new Scanner(System.in);
		int N = stdIn.nextInt();
		int X = stdIn.nextInt();
		int T = stdIn.nextInt();
		System.out.println((N / X + Math.min(1, N % X)) * 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 System.out.println((N / X + Math.min(1, N % X)) * T) System.out.println System.out System System.out (N / X + Math.min(1, N % X)) * T (N / X + Math.min(1, N % X)) N / X N X Math.min(1, N % X) Math.min Math 1 N % X N X T 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();
		System.out.println((N / X + Math.min(1, N % X)) * T);
	}
} 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();
		System.out.println((N / X + Math.min(1, N % X)) * T);
	}
} 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();
		System.out.println((N / X + Math.min(1, N % X)) * T);
	}
}