import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	}
} Main public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	} main {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	} BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); in new BufferedReader(new InputStreamReader(System.in)) String[] tokens = in.readLine().split(" "); tokens in.readLine().split(" ") in.readLine().split in.readLine() in.readLine in " " int n = Integer.parseInt(tokens[0]); n Integer.parseInt(tokens[0]) Integer.parseInt Integer tokens[0] tokens 0 int x = Integer.parseInt(tokens[1]); x Integer.parseInt(tokens[1]) Integer.parseInt Integer tokens[1] tokens 1 int t = Integer.parseInt(tokens[2]); t Integer.parseInt(tokens[2]) Integer.parseInt Integer tokens[2] tokens 2 int ans; ans if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t; n%x == 0 n%x n x 0 ans = n/x*t ans n/x*t n/x n x t ans = (n/x+1)*t ans (n/x+1)*t (n/x+1) n/x n x 1 t System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	}
} public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	}
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tokens = in.readLine().split(" ");
		int n = Integer.parseInt(tokens[0]);
		int x = Integer.parseInt(tokens[1]);
		int t = Integer.parseInt(tokens[2]);
		int ans;
		if (n%x == 0)
			ans = n/x*t;
		else
			ans = (n/x+1)*t;
		System.out.println(ans);
	}
}
