import java.util.*;
import java.lang.*;

public class Main{
    public static void main(String[]args){
	int ans=0;
        Scanner sc = new Scanner(System.in);
        int N=sc.nextInt();
        int X=sc.nextInt();
	int T=sc.nextInt();
        if(N%X==0){
	    ans=T*(N/X);
	}else{
	    ans=T*(N/X+1);
	}
	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