import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scannerS = new Scanner(System.in);
		int N = scannerS.nextInt();
		int X = scannerS.nextInt();
		int T = scannerS.nextInt();

		int a = 0;
		int b = N % X;
		int c = N / X;

		if (b == 0) {
			a = (N / X) * T;
		} else if (b != 0) {
			a = (c + 1) * T;
		}

		System.out.println(a);

	}

}
/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