/**

* @function fibonacci

* @description Fibonacci is the sum of previous two fibonacci numbers.

* @param {Integer} N - The input integer

* @return {Integer} fibonacci of N.

* @see [Fibonacci_Numbers](https://en.wikipedia.org/wiki/Fibonacci_number)

*/

const fibonacci = (N) => {

if (!Number.isInteger(N)) {

throw new TypeError('Input should be integer')

}

// memoize the last two numbers

let firstNumber = 0

let secondNumber = 1

for (let i = 1; i < N; i++) {

const sumOfNumbers = firstNumber + secondNumber

// update last two numbers

firstNumber = secondNumber

secondNumber = sumOfNumbers

}

return N ? secondNumber : firstNumber

}

export { fibonacci }