Fibonacci

Problem

Find the Nth number in Fibonacci sequence.

A Fibonacci sequence is defined as follow:

The first two numbers are 0 and 1. The i th number is the sum of i-1 th number and i-2 th number. The first ten numbers in Fibonacci sequence is:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ...

Example

Given 1, return 0

Given 2, return 1

Given 10, return 34

Note

The Nth fibonacci number won't exceed the max value of signed 32-bit integer in the test cases.