private void btnDeposit_Click(object sender, EventArgs e)
{
string amount = Interaction.InputBox("please, insert the amount what you could deposit.", "do a deposit");
Users user = SUsers.getInstance();
user.Bank.deposit(Convert.ToDouble(amount));
cBank.updateBank(user.Bank);
MessageBox.Show("cash added!!!", "successful operation");
Principal_Load(sender, e);
}