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contracts...contracts 01...13_Errors.sol

pragma solidity 0.5.11;

contract Errors {
    uint public balance;
    uint public constant MAXAMOUNT = 2 ** 256 -1;

    function deposit(uint _amount) external {
        uint oldBalance = balance;
        uint newBalance = balance + _amount;
        require(newBalance >= balance, "Error");
        balance = newBalance;
        assert(balance >= oldBalance);
    }

    function withdraw(uint _amount) external {
        uint oldBalance = balance;
        if (balance < _amount) {
            revert("Not enough funds");
        }
        uint newBalance = balance - _amount;
        require(newBalance <= balance, "Error");
        balance = newBalance;
        assert(balance <= oldBalance);
    }
}