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

public class Main{
	public static void main(String[] args)throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main{
	public static void main(String[] args)throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	}
} Main public static void main(String[] args)throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String[] strs = br.readLine().split(" "); strs br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " int n = Integer.parseInt(strs[0]); n Integer.parseInt(strs[0]) Integer.parseInt Integer strs[0] strs 0 int x = Integer.parseInt(strs[1]); x Integer.parseInt(strs[1]) Integer.parseInt Integer strs[1] strs 1 int t = Integer.parseInt(strs[2]); t Integer.parseInt(strs[2]) Integer.parseInt Integer strs[2] strs 2 System.out.println((int)(Math.ceil((double)n/x)*t) ) System.out.println System.out System System.out (int)(Math.ceil((double)n/x)*t) Math.ceil((double)n/x) Math.ceil Math (double)n/x (double)n x t String[] args args public class Main{
	public static void main(String[] args)throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	}
} public class Main{
	public static void main(String[] args)throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	}
} Main
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main{
	public static void main(String[] args)throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strs = br.readLine().split(" ");
		
		int n = Integer.parseInt(strs[0]);
		int x = Integer.parseInt(strs[1]);
		int t = Integer.parseInt(strs[2]);
		
		System.out.println((int)(Math.ceil((double)n/x)*t) );
		
	}
}
