Write a program to find lines containing 4 digits string ending with 0.
The string must be separated by regular spaces. The only exception is the begging
or the end of the whole line.
Digit is one of the '0123456789' characters.

Do not use regular expressions, just the simplest capabilities
of a programming language!

POINTS: 6
DEADLINE: 2021-02-22 23:59:59