function solve (user){
    let username = user[0];
    let password = '';

    for (let i = username.length - 1; i >=0; i--){
        password +=username[i];
    }
    let counter = 1;
    for (let i = 1; i <= user.length - 1; i++, counter++){
        let currentUsername = user[i];
            if (currentUsername === password){
                console.log(`User ${username} logged in.`);
                break;
            }

            if (counter === 4){
                console.log(`User ${username} blocked!`);
            }else {
                console.log(`Incorrect password. Try again.`);
            }
        }
}