import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		
		int n = scan.nextInt();
		int x = scan.nextInt();
		int t = scan.nextInt();
		
		if(n%x == 0) {
			System.out.println((n/x)*t);
		}else {
			System.out.println(((n/x)+1)*t);
		}
		
		
	}
	
	
	public static int gcd(int x,int y) {
		if(x%y == 0) {
			return y;
		}else {
			return gcd(y,x%y);
		}
	}
}
 




/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz