Each new term in the Fibonacci sequence is generated by adding the previous two terms. By
 starting with 1 and 2, the first 10 terms will be:

             1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

 By considering the terms in the Fibonacci sequence whose values do not exceed four million,
 find the sum of the even-valued terms.


This is a command line program and to run the program type:

perl fibonacci_sum.pl 15 

where the number is the number of digits in the sequence.