In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

Ex Input:
Reverse osmosis uses three to ten gallons of water to produce _ gallon of drinking water.

Ex Output:
one


Ex Input:
Scientists use a characteristic to classify animals into _ groups.

Ex Output:
two


Ex Input:
Fat grams contain nine calories, but carbohydrate grams contain only _ calories.

Ex Output:

four