contract BitcoinusToken is ERC20, Ownable {
  using SafeMath for uint256;

  string public constant name = "Bitcoinus";
    string public constant symbol = "BITS";
    uint8 public constant decimals = 18;

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

  event Mint(address indexed to, uint256 amount);
    event MintFinished();

  bool public mintingFinished = false;

  modifier canTransfer() {
    require(mintingFinished);
    _;
  }

  /**
  * @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 canTransfer returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);

    // SafeMath.sub will throw if there is not enough balance.
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    Transfer(msg.sender, _to, _value);
    return true;
  }

  /**
  * @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 balance) {
    return balances[_owner];
  }


  /**
  * @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 canTransfer 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);
    Transfer(_from, _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;
    Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
  * @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 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, uint _addedValue) public returns (bool) {
    allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
    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, uint _subtractedValue) public returns (bool) {
    uint oldValue = allowed[msg.sender][_spender];
    if (_subtractedValue > oldValue) {
      allowed[msg.sender][_spender] = 0;
    } else {
      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    }
    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

  modifier canMint() {
    require(!mintingFinished);
    _;
  }

  /**
  * @dev Function to mint tokens
  * @param _to The address that will receive the minted tokens.
  * @param _amount The amount of tokens to mint.
  * @return A boolean that indicates if the operation was successful.
  */
  function mint(address _to, uint256 _amount) onlyOwner canMint public returns (bool) {
    totalSupply = totalSupply.add(_amount);
    balances[_to] = balances[_to].add(_amount);
    Mint(_to, _amount);
    Transfer(address(0), _to, _amount);
    return true;
  }

  /**
  * @dev Function to stop minting new tokens.
  * @return True if the operation was successful.
  */
  function finishMinting() onlyOwner canMint public returns (bool) {
    mintingFinished = true;
    MintFinished();
    return true;
  }
}
function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
  uint oldValue = allowed[msg.sender][_spender];
  if (_subtractedValue > oldValue) {
    allowed[msg.sender][_spender] = 0;
  } else {
    allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
  }
  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.
 */