const xhr = new XMLHttpRequest()
xhr.open('GET', 'http://www.wechall.net/challenge/training/programming1/index.php?action=request')
xhr.send(null)
xhr.onreadystatechange = () => {
    const DONE = 4
    const OK = 200
    if (xhr.readyState === DONE) {
        if (xhr.status === OK) {
            const flag = xhr.responseText
            window.location.href = 'http://www.wechall.net/challenge/training/programming1/index.php?answer=' + flag
        } else {
            console.log('Error: '+ xhr.status)
        }
    }
}