Definition: The task is to read a passage and convert numbers in their text forms into digit forms. The text numbers can be used to represent Quantity, Dates and Time, Addresses or Positions.

Positive Example 1 -
Input: Jacob ate three burgers today.
Output: Jacob ate 3 burgers today.

Positive Example 2 -
Input: The Great Depression happened in eighteen twenty one.
Output: The Great Depression happened in 1821.

Negative Example 1 -
Input: My grandfather is sixty seven years old.
Output: My grandfather is 60 7 years old.

Negative Example 2 -
Input: Marie placed sixty fifth in class.
Output: Marie placed 123rd in class.

Now complete the following example -
Input: Oswald apparently started reading about communism when he was about fifteen.
Output: 

 Oswald apparently started reading about communism when he was about 15.