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();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	}
} 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();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	}
} 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();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	} main {
		Scanner stdIn = new Scanner(System.in);
		int N = stdIn.nextInt();
		int X = stdIn.nextInt();
		int T = stdIn.nextInt();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	} 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 sum = 0; sum 0 int ans = 0; ans 0 ans = N / X ans N / X N X sum = N % X sum N % X N X if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		} sum == 0 sum 0 {
			System.out.println(T * ans);
		} System.out.println(T * ans) System.out.println System.out System System.out T * ans T ans {
			ans = ans + 1;
			System.out.println(T * ans);
		} ans = ans + 1 ans ans + 1 ans 1 System.out.println(T * ans) System.out.println System.out System System.out T * ans T ans stdIn.close() stdIn.close stdIn 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();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	}
} 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();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	}
} 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();
		int sum = 0;
		int ans = 0;
		ans = N / X;
		sum = N % X;
		if(sum == 0){
			System.out.println(T * ans);
		}
		else{
			ans = ans + 1;
			System.out.println(T * ans);
		}
		stdIn.close();
	}
}
