import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	}

	private static void solve(int n, int x, int t) {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	}

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

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	}

	private static void solve(int n, int x, int t) {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	}

} Main public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	} main {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	} 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 solve(N, X, T) solve N X T String[] args args private static void solve(int n, int x, int t) {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	} solve {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	} if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		} x == 1 || n == 1 x == 1 x 1 n == 1 n 1 System.out.println(n * t) System.out.println System.out System System.out n * t n t {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		} int r = (n  + x - 1) / x; r (n  + x - 1) / x (n  + x - 1) n  + x n x 1 x System.out.println(r * t) System.out.println System.out System System.out r * t r t int n n int x x int t t public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	}

	private static void solve(int n, int x, int t) {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	}

} public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	}

	private static void solve(int n, int x, int t) {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int X = sc.nextInt();
		int T = sc.nextInt();
		solve(N, X, T);
	}

	private static void solve(int n, int x, int t) {
		// TODO Auto-generated method stub
		if (x == 1 || n == 1) System.out.println(n * t);
		else {
			int r = (n  + x - 1) / x;
			System.out.println(r * t);
		}
	}

}
