1.The Fibonacci numbers are a series of numbers that exhibit the following pattern:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...

The series starts with 0 and 1, and each subsequent number in the series is the sum of the previous two numbers. The Fibonacci sequence, F_n, is defined by the following recurrence relation:

F_n = F_n-1 + F_n-2

Where the initial values are F₀ = 0 and F₁ = 1. Program should prompts the user to enter in a positive integer N and generates the Nth Fibonacci number. main function should handle user input and pass that data to a function called Fib that takes integer N as input and returns the Nth Fibonacci number. Include the functions preconditions and postconditions as comments in the source code. Include some basic input validation to make sure the function's preconditions are met before the function is called. Show the source code and a sample of the program output.