import java.util.Scanner;

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

} import java.util.Scanner; Scanner 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 answer = (N/X)*T;
		if(N%X!=0) {
			answer += T;
		}
		System.out.println(answer);
	}

} 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 answer = (N/X)*T;
		if(N%X!=0) {
			answer += T;
		}
		System.out.println(answer);
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();

		int answer = (N/X)*T;
		if(N%X!=0) {
			answer += T;
		}
		System.out.println(answer);
	} 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 answer = (N/X)*T; answer (N/X)*T (N/X) N X T if(N%X!=0) {
			answer += T;
		} N%X!=0 N%X N X 0 {
			answer += T;
		} answer += T answer T System.out.println(answer) System.out.println System.out System System.out answer 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 answer = (N/X)*T;
		if(N%X!=0) {
			answer += T;
		}
		System.out.println(answer);
	}

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

} Main
import java.util.Scanner;

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

}
