Write a python program that takes a date as input and outputs the date's season in the northern hemisphere. The input is a string to represent the month and an int to represent the day.

Example: If the input is: April 11 the output is: Spring In addition, check if the string and int are valid (an actual month and day). If the input is: Blue 65 the output is: Invalid

The dates for each season in the northern hemisphere are:

Spring: March 20 - June 20

Summer: June 21 - September 21

Autumn: September 22 - December 20

Winter: December 21 - March 19