import java.util.*;
import static java.lang.System.*;

class Main{
  public static void main(String[] a){
    Scanner sc = new Scanner(in);
    int n = sc.nextInt();
    int x = sc.nextInt();
    int t = sc.nextInt();
    
    int y = (n+x-1)/x;
    out.print(y * t);
  }
}
/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