import java.util.Scanner;
public class Main{

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ

		Scanner sc= new Scanner(System.in);
		int n =sc.nextInt();
    	int x=sc.nextInt();
	    int t=sc.nextInt();

	    int min =0;

	    for(;n>0;n=n-x) {
		min=min+t;
	   }
	    System.out.println(min);
	  }

}
/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