nth Fibonacci number

Write a function that computes the nth Fibonacci number. Your function should be called fib() and should take as input a single integer value n, and should return a single integer value representing the nth Fibonacci number.

Go by the definition of \(F_{n}\) here.

Test your code against the following inputs:

n = 5
print(f"Fibonacci number {n} is equal to {fib(n)}")

Fibonacci number 5 is equal to 5

n = 10
print(f"Fibonacci number {n} is equal to {fib(n)}")

Fibonacci number 10 is equal to 55

n = 20
print(f"Fibonacci number {n} is equal to {fib(n)}")

Fibonacci number 20 is equal to 6765

n = 100
print(f"Fibonacci number {n} is equal to {fib(n)}")

Fibonacci number 100 is equal to 354224848179261915075

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sample solution