Project Euler - problem 25

What is the index of the first term in the Fibonacci sequence to contain 1000 digits?

The Fibonacci Sequence is calculated by applying the formula:

Fn = Fn−1 + Fn−2, where F1 = 1 and F2 = 1

(CM): this is one of those deceptive problems that could be solved in a few lines. Recursion will not work well, as only the last two members of the sequence have to be considered to calculate the next member of the sequence.