function fibonacci(n) {
    let firstNum = 0;
    let secondNum = 1;

    if (n > 2) {
        for (let i = 3; i <= n; i++) {
            let currentNum = firstNum + secondNum;

            firstNum = secondNum;
            secondNum = currentNum;
        }

        return secondNum;
    } else if (n === 1) {
        return firstNum;
    } else if (n === 2) {
        return secondNum;
    }
}