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) );
		
	}
}

/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