function preparePayment() public
    {
        uint totalInteres = getInteres(msg.sender);
        uint paidInteres = user[msg.sender].paidInteres;
        if (totalInteres > paidInteres)
        {
            uint amount = totalInteres.sub(paidInteres);

            emit LogPreparePayment(msg.sender, totalInteres, paidInteres, amount);

            user[msg.sender].paidInteres = user[msg.sender].paidInteres.add(amount);
            transfer(msg.sender, amount);
        }
        else
        {
            emit LogSkipPreparePayment(msg.sender, totalInteres, paidInteres);
        }
    }