import java.util.*;

public class Main {
	public static void main(String args[]) {
		
		Scanner ob = new Scanner(System.in);
		int N = ob.nextInt();
		int X = ob.nextInt();
		int T = ob.nextInt();
		int result = 0;
		
		while(N > 0) {
			N -= X;
			result += T;
		}
		System.out.println(result);
		ob.close();
	}
}

/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