IN PYTHON Write a function to compute the nth Fibonacci number.
A Fibonacci sequence is a sequence of numbers where each successive number is the sum of the previous two. The classic Fibonacci sequence begins as 1, 1, 2, 3, 5, 8, 13, ...
Then write a main program that prompts the user to enter n and prints out the nth Fibonacci number. For example, if the user enters 6, then it should print out 8.