import java.io.*;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int t=1;//sc.nextInt();
		while(t-->0) {
			int n=sc.nextInt();
			int x=sc.nextInt();
			int T=sc.nextInt();
			int val=n/x+(n%x==0? 0:1);
			System.out.println(val*T);
		}

	}

}
/*class Reader{
	BufferedReader reader;
	Reader(){
		reader=new BufferedReader(new InputStreamReader(System.in));
	}
	int nextInt() throws IOException{
		String in=reader.readLine().trim();
		return Integer.parseInt(in);
	}
	long nextLong() throws IOException{
		String in=reader.readLine().trim();
		return Long.parseLong(in);
	}
	String next() throws IOException{
		return reader.readLine().trim();
	}
	String[] stringArray() throws IOException{
		return reader.readLine().trim().split("\\s+");
	}
	int[] intArray() throws IOException{
		String[] inp=this.stringArray();
		int[] arr=new int[inp.length];
		int i=0;
		for(String s:inp) {
			arr[i++]=Integer.parseInt(s);
		}
		return arr;
	}
}*/



/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