function solve() {

    let title = document.querySelector('body > form > input[type=text]:nth-child(2)');
    let year = document.querySelector('body > form > input[type=number]:nth-child(4)');
    let price = document.querySelector('body > form > input[type=number]:nth-child(6)');
    let addBtn = document.querySelector('body > form > button');
    let newBook = document.querySelector('#outputs > section:nth-child(2) > div');
    let oldBook = document.querySelector('#outputs > section:nth-child(1) > div');
    let totalProfit = document.querySelector('body > h1:nth-child(3)');
    let priceX = 0;
    let allBtns = document.getElementsByTagName('button');
    let obj = {};

    addBtn.addEventListener('click', addNewItem);

    function addNewItem(e) {
        e.preventDefault();

        if (Number(year.value) > 0 && Number(price.value) > 0 && title.value.length > 0) {

            obj[`${title.value} [${year.value}]`] = price.value;

            if (Number(year.value) >= 2000) {
                // new year
                let div = document.createElement('DIV');
                div.className = "book";

                let p = document.createElement('P');
                p.textContent = `${title.value} [${year.value}]`;

                let btnBuy = document.createElement('Button');
                btnBuy.textContent = `Buy it only for ${price.value} BGN`;
                // btnBuy.className = "buy";

                let btnMove = document.createElement('Button');
                btnMove.textContent = `Move to old section`;
                // btnMove.className = "move";

                div.appendChild(p);
                div.appendChild(btnBuy);
                div.appendChild(btnMove);
                newBook.appendChild(div);

            } else {
                // old year
                let div = document.createElement('DIV');
                div.className = "book";

                let p = document.createElement('P');
                p.textContent = `${title.value} [${year.value}]`;

                let btnBuy = document.createElement('Button');
                btnBuy.textContent = `Buy it only for ${(price.value * 0.85).toFixed(2)} BGN`;
                // btnBuy.className = "buy";

                div.appendChild(p);
                div.appendChild(btnBuy);
                oldBook.appendChild(div);

            }

            Array.from(allBtns).forEach(singleBtn => {

                let firstLetter = singleBtn.textContent[0];

                if (firstLetter === "M") {
                    singleBtn.addEventListener('click', moveIt);

                    function moveIt() {

                        let name = singleBtn.parentElement.firstChild.textContent;
                        let newPrice = obj[name] * 0.85;
                        obj[name] = newPrice;
                        let myBtn = singleBtn.parentElement.childNodes[1];
                        myBtn.textContent = `Buy it only for ${obj[name].toFixed(2)} BGN`;
                        oldBook.appendChild(singleBtn.parentElement);
                        ee.target.style.display = "none";

                    }
                }

                if (firstLetter === "B") {
                    singleBtn.addEventListener('click', buyIt);

                    function buyIt() {

                        let name = singleBtn.parentElement.firstChild.textContent;
                        let number = Number(obj[name]);
                        priceX += number;
                        totalProfit.textContent = `Total Store Profit: ${priceX.toFixed(2)} BGN`;
                        singleBtn.parentElement.style.display = "none";

                    }
                }

            });
        }

    }

}