//package abc176;

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[] ip = br.readLine().split(" ");
		
		int N = Integer.parseInt(ip[0]);
		int X = Integer.parseInt(ip[1]);
		int T = Integer.parseInt(ip[2]);
		
		int ans = N/X*T;
		
		if(N%X != 0) ans += T;
		
		System.out.println(ans);
	}
	
}

/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