Big Fibonacci Numbers
A Fibonacci sequence is calculated by adding the previous two members
of the sequence, with the first two members being both 1.
f (1) = 1, f (2) = 1, f (n >
2) = f (n - 1) + f (n - 2)
Input and Output
Your task is to take numbers as input (one per line), and print the corresponding
Fibonacci number. No generated fibonacci number in excess of 1000 digits
will be in the test data, i.e. f (20) = 6765 has 4 digits.