import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Main {


    public static void main(String[] args) throws IOException {
    
    	Scanner scan = new Scanner(System.in);
    	
    	
    	int n = scan.nextInt();
    	int x = scan.nextInt();
    	int t = scan.nextInt();
    	
    	
    	int time = 0;
    	
    	while (n > 0) {
    		n -= x;
    		time += t;
    	}
    
    	System.out.println(time);
    	
    	
    	
    	
    	}
}

/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