Write a program to find lines containing date ranges in format 'XXXX - XXXX' or 'XXXX-XXXX',
where X is a digit. Digit is one of the '0123456789' characters.
The string must be separated by regular spaces. The only exception is the begging
or the end of the whole line.

Make use of regular expressions.

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DEADLINE: 2021-02-22 23:59:59