function solve() {
    let buttons = document.getElementsByTagName('button');
    buttons[0].addEventListener('click', encode);
    buttons[1].addEventListener('click', decode);

    let inputFields = document.getElementsByTagName('textarea');
    let encodeInputField = inputFields[0];
    let decodeInputField = inputFields[1];

    function encode() {
        let message = encodeInputField.value;

        if (message) {
            let encodedMessage = '';

            for (var i = 0; i < message.length; i++) {
                let currentAsciiCode =  message[i].charCodeAt();
                let currentSymbol = String.fromCharCode((currentAsciiCode + 1));
                encodedMessage += currentSymbol;
              }
            decodeInputField.value = encodedMessage;
            encodeInputField.value = '';
        }
    }

    function decode() {
        let message  = decodeInputField.value;

        if (message) {
            let decodedMeesage = '';

            for (var i = 0; i < message.length; i++) {
                let currentAsciiCode =  message[i].charCodeAt();
                let currentSymbol = String.fromCharCode((currentAsciiCode - 1));
                decodedMeesage += currentSymbol;
              }
            decodeInputField.value = decodedMeesage;
        }
    }
}