pragma solidity ^0.4.24;



library SafeMath {

  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
    if (a == 0) {
      return 0;
    }

    c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    return a / b;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }

}



contract ERC20Basic {

  function totalSupply() public view returns (uint256);

  function balanceOf(address who) public view returns (uint256);

  function transfer(address to, uint256 value) public returns (bool);

  event Transfer(address indexed from, address indexed to, uint256 value);

}



contract ERC20 is ERC20Basic {

  function allowance(address owner, address spender)
    public view returns (uint256);

  function transferFrom(address from, address to, uint256 value)
    public returns (bool);

  function approve(address spender, uint256 value) public returns (bool);

  event Approval(
    address indexed owner,
    address indexed spender,
    uint256 value
  );

}



contract Ownable {

  address public owner;

  event OwnershipRenounced(address indexed previousOwner);

  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );

  constructor() public {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  modifier validAddress {
    assert(0x0 != msg.sender);
    _;
  }

  function transferOwnership(address _newOwner) public onlyOwner validAddress {
    _transferOwnership(_newOwner);
  }

  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }

}



contract BasicToken is ERC20Basic, Ownable {

  using SafeMath for uint256;

  mapping(address => uint256) balances;

  uint256 totalSupply_;

  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);
    require(_value > 0);

    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

  function balanceOf(address _owner) public view returns (uint256) {
    return balances[_owner];
  }

  event Burn(address indexed burner, uint256 value);

  function burn(uint256 _value) public {
    _burn(msg.sender, _value);
  }

  function _burn(address _who, uint256 _value) internal {
    require(_value <= balances[_who]);

    balances[_who] = balances[_who].sub(_value);
    totalSupply_ = totalSupply_.sub(_value);

    emit Burn(_who, _value);
    emit Transfer(_who, address(0), _value);
  }

}



contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) internal allowed;

  function transferFrom(
    address _from,
    address _to,
    uint256 _value
  )
    public validAddress
    returns (bool)
  {
    require(_to != address(0));
    require(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);
    require(_value > 0);

    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;
  }

  function approve(address _spender, uint256 _value) public validAddress returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  function allowance(
    address _owner,
    address _spender
   )
    public
    view
    returns (uint256)
  {
    return allowed[_owner][_spender];
  }

  function increaseApproval(
    address _spender,
    uint256 _addedValue
  )
    public validAddress
    returns (bool)
  {
    allowed[msg.sender][_spender] = (
      allowed[msg.sender][_spender].add(_addedValue));
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

  function transferTokens(address _from, address _to, uint256 _value) public validAddress onlyOwner returns (bool) {
    require(_to != address(0));
    require(_value <= balances[_from]);
    require(_value > 0);

    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(_from, _to, _value);
    return true;
  }

  function decreaseApproval(
    address _spender,
    uint256 _subtractedValue
  )
    public validAddress
    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 GOEXToken is StandardToken {

  string public constant name = "GOEX Token";
  string public constant symbol = "GOEX";
  uint8 public constant decimals = 18;

  uint256 public constant INITIAL_SUPPLY = 500000000 * (10 ** uint256(decimals));

  constructor() public {
    totalSupply_ = INITIAL_SUPPLY;
    balances[msg.sender] = INITIAL_SUPPLY;
    emit Transfer(address(0), msg.sender, INITIAL_SUPPLY);
  }

}