import java.util.Scanner;
 
public class Main{
 
    public static void main(String[] args) {
        Scanner s  = new Scanner(System.in);
        int N,x,t;
        N = s.nextInt();
        x = s.nextInt();
        t = s.nextInt();
        int count = 0;
        while(N>0){
            N = N-x;
            count++;
        }
        int result = count * t;
 
        System.out.println(result);
    }
}
/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