import java.util.Scanner;

public class Main {
	
	public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		
		int N = scanner.nextInt();
		int X = scanner.nextInt();
		int T = scanner.nextInt();
		
		scanner.close();
		
		int result = N / X;
		int amari = N % X;
		
		if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		}
	}

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

} Main public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		
		int N = scanner.nextInt();
		int X = scanner.nextInt();
		int T = scanner.nextInt();
		
		scanner.close();
		
		int result = N / X;
		int amari = N % X;
		
		if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		}
	} main {
		
		Scanner scanner = new Scanner(System.in);
		
		int N = scanner.nextInt();
		int X = scanner.nextInt();
		int T = scanner.nextInt();
		
		scanner.close();
		
		int result = N / X;
		int amari = N % X;
		
		if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		}
	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int N = scanner.nextInt(); N scanner.nextInt() scanner.nextInt scanner int X = scanner.nextInt(); X scanner.nextInt() scanner.nextInt scanner int T = scanner.nextInt(); T scanner.nextInt() scanner.nextInt scanner scanner.close() scanner.close scanner int result = N / X; result N / X N X int amari = N % X; amari N % X N X if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		} amari == 0 amari 0 {
			System.out.println(result * T);
		} System.out.println(result * T) System.out.println System.out System System.out result * T result T {
			System.out.println(result * T + T);
		} System.out.println(result * T + T) System.out.println System.out System System.out result * T + T result * T result T T String[] args args public class Main {
	
	public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		
		int N = scanner.nextInt();
		int X = scanner.nextInt();
		int T = scanner.nextInt();
		
		scanner.close();
		
		int result = N / X;
		int amari = N % X;
		
		if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		}
	}

} public class Main {
	
	public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		
		int N = scanner.nextInt();
		int X = scanner.nextInt();
		int T = scanner.nextInt();
		
		scanner.close();
		
		int result = N / X;
		int amari = N % X;
		
		if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		}
	}

} Main
import java.util.Scanner;

public class Main {
	
	public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		
		int N = scanner.nextInt();
		int X = scanner.nextInt();
		int T = scanner.nextInt();
		
		scanner.close();
		
		int result = N / X;
		int amari = N % X;
		
		if (amari == 0) {
			System.out.println(result * T);
		} else {
			System.out.println(result * T + T);
		}
	}

}
