function login(input) {
    let username = input.shift();
    let password = input.shift();
    let output = "";
    let counter = 0;

    for (let j = 1; j <= 4; j++) {
        for (let i = username.length - 1; i >= 0; i--) {
            a = username.charCodeAt(i);
            output += `${String.fromCharCode(a)}`;
            output = output.trim();
        }
        if (password != output && counter<3) {
            console.log("Incorrect password. Try again.");

        } else if (password == output) {
            console.log(`User ${username} logged in.`);
            break;
        }
        if (counter == 3) {
            console.log(`User ${username} blocked!`);
            break;
        }
        counter++;
        output = "";
        password = input.shift();
    }
}