// Vulnerability label: clean
pragma solidity ^0.5.0;


library SafeMath {

    uint256 constant internal MAX_UINT = 2 ** 256 - 1; // max uint256

    /**
     * @dev Multiplies two numbers, reverts on overflow.
     */
    function mul(uint256 _a, uint256 _b) internal pure returns(uint256) {
        if (_a == 0) {
            return 0;
        }
        require(MAX_UINT / _a >= _b);
        return _a * _b;
    }

    /**
     * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
     */
    function div(uint256 _a, uint256 _b) internal pure returns(uint256) {
        require(_b != 0);
        return _a / _b;
    }

    /**
     * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 _a, uint256 _b) internal pure returns(uint256) {
        require(_b <= _a);
        return _a - _b;
    }

    /**
     * @dev Adds two numbers, reverts on overflow.
     */
    function add(uint256 _a, uint256 _b) internal pure returns(uint256) {
        require(MAX_UINT - _a >= _b);
        return _a + _b;
    }

}


contract Ownable {
    address public owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param _newOwner The address to transfer ownership to.
     */
    function transferOwnership(address _newOwner) public onlyOwner {
        _transferOwnership(_newOwner);
    }

    /**
     * @dev Transfers control of the contract to a newOwner.
     * @param _newOwner The address to transfer ownership to.
     */
    function _transferOwnership(address _newOwner) internal {
        require(_newOwner != address(0));
        emit OwnershipTransferred(owner, _newOwner);
        owner = _newOwner;
    }
}

contract Pausable is Ownable {
    event Pause();
    event Unpause();

    bool public paused = false;

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!paused);
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     */
    modifier whenPaused() {
        require(paused);
        _;
    }

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() public onlyOwner whenNotPaused {
        paused = true;
        emit Pause();
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() public onlyOwner whenPaused {
        paused = false;
        emit Unpause();
    }
}


contract StandardToken {
    using SafeMath for uint256;

    mapping(address => uint256) internal balances;

    mapping(address => mapping(address => uint256)) internal allowed;

    uint256 internal totalSupply_;

    event Transfer(
        address indexed from,
        address indexed to,
        uint256 value
    );

    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 vaule
    );

    /**
     * @dev Total number of tokens in existence
     */
    function totalSupply() public view returns(uint256) {
        return totalSupply_;
    }

    /**
     * @dev Gets the balance of the specified address.
     * @param _owner The address to query the the balance of.
     * @return An uint256 representing the amount owned by the passed address.
     */
    function balanceOf(address _owner) public view returns(uint256) {
        return balances[_owner];
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param _owner address The address which owns the funds.
     * @param _spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(
        address _owner,
        address _spender
    )
    public
    view
    returns(uint256) {
        return allowed[_owner][_spender];
    }

    /**
     * @dev Transfer token for a specified address
     * @param _to The address to transfer to.
     * @param _value The amount to be transferred.
     */
    function transfer(address _to, uint256 _value) public returns(bool) {
        require(_to != address(0));
        require(_value <= balances[msg.sender]);

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */
    function approve(address _spender, uint256 _value) public returns(bool) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @dev Transfer tokens from one address to another
     * @param _from address The address which you want to send tokens from
     * @param _to address The address which you want to transfer to
     * @param _value uint256 the amount of tokens to be transferred
     */
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    returns(bool) {
        require(_to != address(0));
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed[_spender] == 0. To increment
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * @param _spender The address which will spend the funds.
     * @param _addedValue The amount of tokens to increase the allowance by.
     */
    function increaseApproval(
        address _spender,
        uint256 _addedValue
    )
    public
    returns(bool) {
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed[_spender] == 0. To decrement
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * @param _spender The address which will spend the funds.
     * @param _subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseApproval(
        address _spender,
        uint256 _subtractedValue
    )
    public
    returns(bool) {
        uint256 oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue >= oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
}


contract BurnableToken is StandardToken, Ownable {

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account. Uses the internal burn function.
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0)); 
        totalSupply_ = totalSupply_.sub(value);
        balances[account] = balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Burns a specific amount of tokens.
     * @param value The amount of token to be burned.
     */
    function burn(uint256 value) public onlyOwner{
        _burn(msg.sender, value);
    }
}


contract PausableToken is StandardToken, Pausable {

    function transfer(
        address _to,
        uint256 _value
    )
    public
    whenNotPaused
    returns(bool) {
        return super.transfer(_to, _value);
    }

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    whenNotPaused
    returns(bool) {
        return super.transferFrom(_from, _to, _value);
    }

    function approve(
        address _spender,
        uint256 _value
    )
    public
    whenNotPaused
    returns(bool) {
        return super.approve(_spender, _value);
    }

    function increaseApproval(
        address _spender,
        uint _addedValue
    )
    public
    whenNotPaused
    returns(bool success) {
        return super.increaseApproval(_spender, _addedValue);
    }

    function decreaseApproval(
        address _spender,
        uint _subtractedValue
    )
    public
    whenNotPaused
    returns(bool success) {
        return super.decreaseApproval(_spender, _subtractedValue);
    }
}


/**
 * @title ZBMegaToken token
 * @dev Initialize the basic information of ZBMegaToken.
 */
contract ZBMegaToken is PausableToken, BurnableToken {
    string public constant name = "ZB Mega"; // name of Token
    string public constant symbol = "ZM"; // symbol of Token
    uint8 public constant decimals = 18; // decimals of Token
    uint256 constant _INIT_TOTALSUPPLY = 860000000;

  /**
   * @dev constructor Initialize the basic information.
   */
    constructor() public {
        totalSupply_ = _INIT_TOTALSUPPLY * 10 ** uint256(decimals);
        owner = 0x1Acfb5Fb2aa33C0fc0d7f94A4099aff6EA8d368C;
        balances[owner] = totalSupply_;
    }
}