Help finding duplicates

Sample - Copy.xlsx

Hi all, I'm using Excel 2013, I have a table that has 116,000 rows , The first Column is repeated numbers for wells, the second column is months of production. Now my problem is that there is 2600 months that is repeated for the same well numbers. How would I highlight them or copy them to a different file?
For example in the next table, I'm trying to find a function to find the bold cells , please note that the letters are the first column and the numbers are the second column.

A 1
A 2
A 3
A 3
A 4
B 1
B 2
B 3
B 4
B 4
C 1
C 1
C 2
C 2
C 3
Thank you very much for any help!