important decision so when you are doing feature engineering use it for example I GPM and you have lots of teachers that may be used to do feature engineering it's very difficult to tribe or combinations with all teachers you may end up with thousands and thousands of pizza before finding boss that may help you so one thing that's I usually don't I find it quite useful is that I make a neural network and the gradient boosting decision tree I have two scores to baseline scores I remove the same feature from both the