pragma solidity 0.4.23;


/**
* @title SafeMath
* @dev Math operations with safety checks that throw on error
*/
library SafeMath {

   /**
    * @dev Multiplies two numbers, throws on overflow.
    */
   function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
       // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
       // benefit is lost if 'b' is also tested.
       // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
       if (a == 0) {
           return 0;
       }

       c = a * b;
       assert(c / a == b);
       return c;
   }

   /**
    * @dev Integer division of two numbers, truncating the quotient.
    */
   function div(uint256 a, uint256 b) internal pure returns (uint256) {
       // assert(b > 0); // Solidity automatically throws when dividing by 0
       // uint256 c = a / b;
       // assert(a == b * c + a % b); // There is no case in which this doesn't hold
       return a / b;
   }

   /**
    * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
    */
   function sub(uint256 a, uint256 b) internal pure returns (uint256) {
       assert(b <= a);
       return a - b;
   }

   /**
    * @dev Adds two numbers, throws on overflow.
    */
   function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
       c = a + b;
       assert(c >= a);
       return c;
   }
}


/**
* Utility library of inline functions on addresses
*/
library AddressUtils {

   /**
    * Returns whether the target address is a contract
    * @dev This function will return false if invoked during the constructor of a contract,
    *  as the code is not actually created until after the constructor finishes.
    * @param addr address to check
    * @return whether the target address is a contract
    */
   function isContract(address addr) internal view returns (bool) {
       uint256 size;
       // XXX Currently there is no better way to check if there is a contract in an address
       // than to check the size of the code at that address.
       // See https://ethereum.stackexchange.com/a/14016/36603
       // for more details about how this works.
       // TODO Check this again before the Serenity release, because all addresses will be
       // contracts then.
       // solium-disable-next-line security/no-inline-assembly
       assembly { size := extcodesize(addr) }
       return size > 0;
   }

}


/**
* @title ERC721 token receiver interface
* @dev Interface for any contract that wants to support safeTransfers
* from ERC721 asset contracts.
*/
contract ERC721Receiver {
   /**
   * @dev Magic value to be returned upon successful reception of an NFT
   *  Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`,
   *  which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
   */
   bytes4 internal constant ERC721_RECEIVED = 0xf0b9e5ba;

   /**
   * @notice Handle the receipt of an NFT
   * @dev The ERC721 smart contract calls this function on the recipient
   * after a `safetransfer`. This function MAY throw to revert and reject the
   * transfer. This function MUST use 50,000 gas or less. Return of other
   * than the magic value MUST result in the transaction being reverted.
   * Note: the contract address is always the message sender.
   * @param _from The sending address
   * @param _tokenId The NFT identifier which is being transfered
   * @param _data Additional data with no specified format
   * @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
   */
   function onERC721Received(address _from, uint256 _tokenId, bytes _data) public returns(bytes4);
}

/**
* @title ERC165
* @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
*/
interface ERC165 {

   /**
    * @notice Query if a contract implements an interface
    * @param _interfaceId The interface identifier, as specified in ERC-165
    * @dev Interface identification is specified in ERC-165. This function
    * uses less than 30,000 gas.
    */
   function supportsInterface(bytes4 _interfaceId) external view returns (bool);
}


/**
* @title ERC721 Non-Fungible Token Standard basic interface
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Basic is ERC165 {
   event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
   event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);
   event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

   function balanceOf(address _owner) public view returns (uint256 _balance);
   function ownerOf(uint256 _tokenId) public view returns (address _owner);
   function exists(uint256 _tokenId) public view returns (bool _exists);

   function approve(address _to, uint256 _tokenId) public;
   function getApproved(uint256 _tokenId) public view returns (address _operator);

   function setApprovalForAll(address _operator, bool _approved) public;
   function isApprovedForAll(address _owner, address _operator) public view returns (bool);

   function transferFrom(address _from, address _to, uint256 _tokenId) public;
   function safeTransferFrom(address _from, address _to, uint256 _tokenId) public;

   function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes _data) public;
}


/**
* @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
* @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Enumerable is ERC721Basic {
   function totalSupply() public view returns (uint256);
   function tokenOfOwnerByIndex(address _owner, uint256 _index) public view returns (uint256 _tokenId);
   function tokenByIndex(uint256 _index) public view returns (uint256);
}


/**
* @title ERC-721 Non-Fungible Token Standard, optional metadata extension
* @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721Metadata is ERC721Basic {
   function name() external view returns (string _name);
   function symbol() external view returns (string _symbol);
   function tokenURI(uint256 _tokenId) public view returns (string);
}


/**
* @title ERC-721 Non-Fungible Token Standard, full implementation interface
* @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721 is ERC721Basic, ERC721Enumerable, ERC721Metadata {

}


contract ERC721Holder is ERC721Receiver {
   function onERC721Received(address, uint256, bytes) public returns(bytes4) {
       return ERC721_RECEIVED;
   }
}


/**
* @title SupportsInterfaceWithLookup
* @author Matt Condon (@shrugs)
* @dev Implements ERC165 using a lookup table.
*/
contract SupportsInterfaceWithLookup is ERC165 {
   bytes4 public constant InterfaceId_ERC165 = 0x01ffc9a7;
   /**
    * 0x01ffc9a7 ===
    *   bytes4(keccak256('supportsInterface(bytes4)'))
    */

   /**
    * @dev a mapping of interface id to whether or not it's supported
    */
   mapping(bytes4 => bool) internal supportedInterfaces;

   /**
    * @dev A contract implementing SupportsInterfaceWithLookup
    * implement ERC165 itself
    */
   constructor() public {
       _registerInterface(InterfaceId_ERC165);
   }

   /**
    * @dev implement supportsInterface(bytes4) using a lookup table
    */
   function supportsInterface(bytes4 _interfaceId) external view returns (bool) {
       return supportedInterfaces[_interfaceId];
   }

   /**
    * @dev private method for registering an interface
    */
   function _registerInterface(bytes4 _interfaceId) internal {
       require(_interfaceId != 0xffffffff);
       supportedInterfaces[_interfaceId] = true;
   }
}


/**
* @title ERC721 Non-Fungible Token Standard basic implementation
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract ERC721BasicToken is SupportsInterfaceWithLookup, ERC721Basic {

   bytes4 private constant InterfaceId_ERC721 = 0x80ac58cd;
   /*
    * 0x80ac58cd ===
    *   bytes4(keccak256('balanceOf(address)')) ^
    *   bytes4(keccak256('ownerOf(uint256)')) ^
    *   bytes4(keccak256('approve(address,uint256)')) ^
    *   bytes4(keccak256('getApproved(uint256)')) ^
    *   bytes4(keccak256('setApprovalForAll(address,bool)')) ^
    *   bytes4(keccak256('isApprovedForAll(address,address)')) ^
    *   bytes4(keccak256('transferFrom(address,address,uint256)')) ^
    *   bytes4(keccak256('safeTransferFrom(address,address,uint256)')) ^
    *   bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)'))
    */

   bytes4 private constant InterfaceId_ERC721Exists = 0x4f558e79;
   /*
    * 0x4f558e79 ===
    *   bytes4(keccak256('exists(uint256)'))
    */

   using SafeMath for uint256;
   using AddressUtils for address;

   // Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
   // which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
   bytes4 constant ERC721_RECEIVED = 0xf0b9e5ba;

   // Mapping from token ID to owner
   mapping (uint256 => address) internal tokenOwner;

   // Mapping from token ID to approved address
   mapping (uint256 => address) internal tokenApprovals;

   // Mapping from owner to number of owned token
   mapping (address => uint256) internal ownedTokensCount;

   // Mapping from owner to operator approvals
   mapping (address => mapping (address => bool)) internal operatorApprovals;

   /**
    * @dev Guarantees msg.sender is owner of the given token
    * @param _tokenId uint256 ID of the token to validate its ownership belongs to msg.sender
    */
   modifier onlyOwnerOf(uint256 _tokenId) {
       require(ownerOf(_tokenId) == msg.sender);
       _;
   }

   /**
    * @dev Checks msg.sender can transfer a token, by being owner, approved, or operator
    * @param _tokenId uint256 ID of the token to validate
    */
   modifier canTransfer(uint256 _tokenId) {
       require(isApprovedOrOwner(msg.sender, _tokenId));
       _;
   }

   constructor() public {
       // register the supported interfaces to conform to ERC721 via ERC165
       _registerInterface(InterfaceId_ERC721);
       _registerInterface(InterfaceId_ERC721Exists);
   }

   /**
    * @dev Gets the balance of the specified address
    * @param _owner address to query the balance of
    * @return uint256 representing the amount owned by the passed address
    */
   function balanceOf(address _owner) public view returns (uint256) {
       require(_owner != address(0));
       return ownedTokensCount[_owner];
   }

   /**
    * @dev Gets the owner of the specified token ID
    * @param _tokenId uint256 ID of the token to query the owner of
    * @return owner address currently marked as the owner of the given token ID
    */
   function ownerOf(uint256 _tokenId) public view returns (address) {
       address owner = tokenOwner[_tokenId];
       require(owner != address(0));
       return owner;
   }

   /**
    * @dev Returns whether the specified token exists
    * @param _tokenId uint256 ID of the token to query the existence of
    * @return whether the token exists
    */
   function exists(uint256 _tokenId) public view returns (bool) {
       address owner = tokenOwner[_tokenId];
       return owner != address(0);
   }

   /**
    * @dev Approves another address to transfer the given token ID
    * @dev The zero address indicates there is no approved address.
    * @dev There can only be one approved address per token at a given time.
    * @dev Can only be called by the token owner or an approved operator.
    * @param _to address to be approved for the given token ID
    * @param _tokenId uint256 ID of the token to be approved
    */
   function approve(address _to, uint256 _tokenId) public {
       address owner = ownerOf(_tokenId);
       require(_to != owner);
       require(msg.sender == owner || isApprovedForAll(owner, msg.sender));

       tokenApprovals[_tokenId] = _to;
       emit Approval(owner, _to, _tokenId);
   }

   /**
    * @dev Gets the approved address for a token ID, or zero if no address set
    * @param _tokenId uint256 ID of the token to query the approval of
    * @return address currently approved for the given token ID
    */
   function getApproved(uint256 _tokenId) public view returns (address) {
       return tokenApprovals[_tokenId];
   }

   /**
    * @dev Sets or unsets the approval of a given operator
    * @dev An operator is allowed to transfer all tokens of the sender on their behalf
    * @param _to operator address to set the approval
    * @param _approved representing the status of the approval to be set
    */
   function setApprovalForAll(address _to, bool _approved) public {
       require(_to != msg.sender);
       operatorApprovals[msg.sender][_to] = _approved;
       emit ApprovalForAll(msg.sender, _to, _approved);
   }

   /**
    * @dev Tells whether an operator is approved by a given owner
    * @param _owner owner address which you want to query the approval of
    * @param _operator operator address which you want to query the approval of
    * @return bool whether the given operator is approved by the given owner
    */
   function isApprovedForAll(address _owner, address _operator) public view returns (bool) {
       return operatorApprovals[_owner][_operator];
   }

   /**
    * @dev Transfers the ownership of a given token ID to another address
    * @dev Usage of this method is discouraged, use `safeTransferFrom` whenever possible
    * @dev Requires the msg sender to be the owner, approved, or operator
    * @param _from current owner of the token
    * @param _to address to receive the ownership of the given token ID
    * @param _tokenId uint256 ID of the token to be transferred
   */
   function transferFrom(address _from, address _to, uint256 _tokenId) public canTransfer(_tokenId) {
       require(_from != address(0));
       require(_to != address(0));

       clearApproval(_from, _tokenId);
       removeTokenFrom(_from, _tokenId);
       addTokenTo(_to, _tokenId);

       emit Transfer(_from, _to, _tokenId);
   }

   /**
    * @dev Safely transfers the ownership of a given token ID to another address
    * @dev If the target address is a contract, it must implement `onERC721Received`,
    *  which is called upon a safe transfer, and return the magic value
    *  `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`; otherwise,
    *  the transfer is reverted.
    * @dev Requires the msg sender to be the owner, approved, or operator
    * @param _from current owner of the token
    * @param _to address to receive the ownership of the given token ID
    * @param _tokenId uint256 ID of the token to be transferred
   */
   function safeTransferFrom(address _from, address _to, uint256 _tokenId) public canTransfer(_tokenId) {
       // solium-disable-next-line arg-overflow
       safeTransferFrom(_from, _to, _tokenId, "");
   }

   /**
    * @dev Safely transfers the ownership of a given token ID to another address
    * @dev If the target address is a contract, it must implement `onERC721Received`,
    *  which is called upon a safe transfer, and return the magic value
    *  `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`; otherwise,
    *  the transfer is reverted.
    * @dev Requires the msg sender to be the owner, approved, or operator
    * @param _from current owner of the token
    * @param _to address to receive the ownership of the given token ID
    * @param _tokenId uint256 ID of the token to be transferred
    * @param _data bytes data to send along with a safe transfer check
    */
   function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes _data) public canTransfer(_tokenId) {
       transferFrom(_from, _to, _tokenId);
       // solium-disable-next-line arg-overflow
       require(checkAndCallSafeTransfer(_from, _to, _tokenId, _data));
   }

   /**
    * @dev Returns whether the given spender can transfer a given token ID
    * @param _spender address of the spender to query
    * @param _tokenId uint256 ID of the token to be transferred
    * @return bool whether the msg.sender is approved for the given token ID,
    *  is an operator of the owner, or is the owner of the token
    */
   function isApprovedOrOwner(
       address _spender,
       uint256 _tokenId
   )
       internal
       view
       returns (bool)
   {
       address owner = ownerOf(_tokenId);
       // Disable solium check because of
       // https://github.com/duaraghav8/Solium/issues/175
       // solium-disable-next-line operator-whitespace
       return (
           _spender == owner ||
           getApproved(_tokenId) == _spender ||
           isApprovedForAll(owner, _spender)
       );
   }

   /**
    * @dev Internal function to mint a new token
    * @dev Reverts if the given token ID already exists
    * @param _to The address that will own the minted token
    * @param _tokenId uint256 ID of the token to be minted by the msg.sender
    */
   function _mint(address _to, uint256 _tokenId) internal {
       require(_to != address(0));
       addTokenTo(_to, _tokenId);
       emit Transfer(address(0), _to, _tokenId);
   }

   /**
    * @dev Internal function to clear current approval of a given token ID
    * @dev Reverts if the given address is not indeed the owner of the token
    * @param _owner owner of the token
    * @param _tokenId uint256 ID of the token to be transferred
    */
   function clearApproval(address _owner, uint256 _tokenId) internal {
       require(ownerOf(_tokenId) == _owner);
       if (tokenApprovals[_tokenId] != address(0)) {
           tokenApprovals[_tokenId] = address(0);
           emit Approval(_owner, address(0), _tokenId);
       }
   }

   /**
    * @dev Internal function to add a token ID to the list of a given address
    * @param _to address representing the new owner of the given token ID
    * @param _tokenId uint256 ID of the token to be added to the tokens list of the given address
    */
   function addTokenTo(address _to, uint256 _tokenId) internal {
       require(tokenOwner[_tokenId] == address(0));
       tokenOwner[_tokenId] = _to;
       ownedTokensCount[_to] = ownedTokensCount[_to].add(1);
   }

   /**
    * @dev Internal function to remove a token ID from the list of a given address
    * @param _from address representing the previous owner of the given token ID
    * @param _tokenId uint256 ID of the token to be removed from the tokens list of the given address
    */
   function removeTokenFrom(address _from, uint256 _tokenId) internal {
       require(ownerOf(_tokenId) == _from);
       ownedTokensCount[_from] = ownedTokensCount[_from].sub(1);
       tokenOwner[_tokenId] = address(0);
   }

   /**
    * @dev Internal function to invoke `onERC721Received` on a target address
    * The call is not executed if the target address is not a contract
    * @param _from address representing the previous owner of the given token ID
    * @param _to target address that will receive the tokens
    * @param _tokenId uint256 ID of the token to be transferred
    * @param _data bytes optional data to send along with the call
    * @return whether the call correctly returned the expected magic value
    */
   function checkAndCallSafeTransfer(
       address _from,
       address _to,
       uint256 _tokenId,
       bytes _data
   )
       internal
       returns (bool)
   {
       if (!_to.isContract()) {
           return true;
       }

       bytes4 retval = ERC721Receiver(_to).onERC721Received(
       _from, _tokenId, _data);
       return (retval == ERC721_RECEIVED);
   }
}


/**
* @title Ownable
* @dev The Ownable contract has an owner address, and provides basic authorization control
* functions, this simplifies the implementation of "user permissions".
*/
contract Ownable {
    address public owner;
    address public pendingOwner;
    address public manager;

    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 Modifier throws if called by any account other than the manager.
     */
    modifier onlyManager() {
        require(msg.sender == manager);
        _;
    }

    /**
     * @dev Modifier throws if called by any account other than the pendingOwner.
     */
    modifier onlyPendingOwner() {
        require(msg.sender == pendingOwner);
        _;
    }

    constructor() public {
        owner = msg.sender;
    }

    /**
     * @dev Allows the current owner to set the pendingOwner address.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        pendingOwner = newOwner;
    }

    /**
     * @dev Allows the pendingOwner address to finalize the transfer.
     */
    function claimOwnership() public onlyPendingOwner {
        emit OwnershipTransferred(owner, pendingOwner);
        owner = pendingOwner;
        pendingOwner = address(0);
    }

    /**
     * @dev Sets the manager address.
     * @param _manager The manager address.
     */
    function setManager(address _manager) public onlyOwner {
        require(_manager != address(0));
        manager = _manager;
    }

}



/**
* @title Full ERC721 Token
* This implementation includes all the required and some optional functionality of the ERC721 standard
* Moreover, it includes approve all functionality using operator terminology
* @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
*/
contract GeneralSecurityToken is SupportsInterfaceWithLookup, ERC721, ERC721BasicToken, Ownable {

   bytes4 private constant InterfaceId_ERC721Enumerable = 0x780e9d63;
   /**
    * 0x780e9d63 ===
    *   bytes4(keccak256('totalSupply()')) ^
    *   bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
    *   bytes4(keccak256('tokenByIndex(uint256)'))
    */

   bytes4 private constant InterfaceId_ERC721Metadata = 0x5b5e139f;
   /**
    * 0x5b5e139f ===
    *   bytes4(keccak256('name()')) ^
    *   bytes4(keccak256('symbol()')) ^
    *   bytes4(keccak256('tokenURI(uint256)'))
    */

   // Token name
   string public name_ = "GeneralSecurityToken";

   // Token symbol
   string public symbol_ = "GST";
  
   uint public tokenIDCount = 0;

   // Mapping from owner to list of owned token IDs
   mapping(address => uint256[]) internal ownedTokens;

   // Mapping from token ID to index of the owner tokens list
   mapping(uint256 => uint256) internal ownedTokensIndex;

   // Array with all token ids, used for enumeration
   uint256[] internal allTokens;

   // Mapping from token id to position in the allTokens array
   mapping(uint256 => uint256) internal allTokensIndex;

   // Optional mapping for token URIs
   mapping(uint256 => string) internal tokenURIs;

   struct Data{
       string information;
       string URL;
   }
  
   mapping(uint256 => Data) internal tokenData;
   /**
    * @dev Constructor function
    */
   constructor() public {


       // register the supported interfaces to conform to ERC721 via ERC165
       _registerInterface(InterfaceId_ERC721Enumerable);
       _registerInterface(InterfaceId_ERC721Metadata);
   }

   /**
    * @dev External function to mint a new token
    * @dev Reverts if the given token ID already exists
    * @param _to address the beneficiary that will own the minted token
    */
   function mint(address _to) external onlyManager {
       _mint(_to, tokenIDCount++);
   }

   /**
    * @dev Gets the token name
    * @return string representing the token name
    */
   function name() external view returns (string) {
       return name_;
   }

   /**
    * @dev Gets the token symbol
    * @return string representing the token symbol
    */
   function symbol() external view returns (string) {
       return symbol_;
   }

   function arrayOfTokensByAddress(address _holder) public view returns(uint256[]) {
       return ownedTokens[_holder];
   }

   /**
    * @dev Returns an URI for a given token ID
    * @dev Throws if the token ID does not exist. May return an empty string.
    * @param _tokenId uint256 ID of the token to query
    */
   function tokenURI(uint256 _tokenId) public view returns (string) {
       require(exists(_tokenId));
       return tokenURIs[_tokenId];
   }

   /**
    * @dev Gets the token ID at a given index of the tokens list of the requested owner
    * @param _owner address owning the tokens list to be accessed
    * @param _index uint256 representing the index to be accessed of the requested tokens list
    * @return uint256 token ID at the given index of the tokens list owned by the requested address
    */
   function tokenOfOwnerByIndex(address _owner, uint256 _index) public view returns (uint256) {
       require(_index < balanceOf(_owner));
       return ownedTokens[_owner][_index];
   }

   /**
    * @dev Gets the total amount of tokens stored by the contract
    * @return uint256 representing the total amount of tokens
    */
   function totalSupply() public view returns (uint256) {
       return allTokens.length;
   }

   /**
    * @dev Gets the token ID at a given index of all the tokens in this contract
    * @dev Reverts if the index is greater or equal to the total number of tokens
    * @param _index uint256 representing the index to be accessed of the tokens list
    * @return uint256 token ID at the given index of the tokens list
    */
   function tokenByIndex(uint256 _index) public view returns (uint256) {
       require(_index < totalSupply());
       return allTokens[_index];
   }

   /**
    * @dev Internal function to set the token URI for a given token
    * @dev Reverts if the token ID does not exist
    * @param _tokenId uint256 ID of the token to set its URI
    * @param _uri string URI to assign
    */
   function _setTokenURI(uint256 _tokenId, string _uri) internal {
       require(exists(_tokenId));
       tokenURIs[_tokenId] = _uri;
   }

   /**
    * @dev Internal function to add a token ID to the list of a given address
    * @param _to address representing the new owner of the given token ID
    * @param _tokenId uint256 ID of the token to be added to the tokens list of the given address
    */
   function addTokenTo(address _to, uint256 _tokenId) internal {
       super.addTokenTo(_to, _tokenId);
       uint256 length = ownedTokens[_to].length;
       ownedTokens[_to].push(_tokenId);
       ownedTokensIndex[_tokenId] = length;
   }

   /**
    * @dev Internal function to remove a token ID from the list of a given address
    * @param _from address representing the previous owner of the given token ID
    * @param _tokenId uint256 ID of the token to be removed from the tokens list of the given address
    */
   function removeTokenFrom(address _from, uint256 _tokenId) internal {
       super.removeTokenFrom(_from, _tokenId);

       uint256 tokenIndex = ownedTokensIndex[_tokenId];
       uint256 lastTokenIndex = ownedTokens[_from].length.sub(1);
       uint256 lastToken = ownedTokens[_from][lastTokenIndex];

       ownedTokens[_from][tokenIndex] = lastToken;
       ownedTokens[_from][lastTokenIndex] = 0;
       // Note that this will handle single-element arrays. In that case, both tokenIndex and lastTokenIndex are
       // going to be zero. Then we can make sure that we will remove _tokenId from the ownedTokens list since we are
       // first swapping the lastToken to the first position, and then dropping the element placed in the last
       // position of the list

       ownedTokens[_from].length--;
       ownedTokensIndex[_tokenId] = 0;
       ownedTokensIndex[lastToken] = tokenIndex;
   }

   /**
    * @dev Internal function to mint a new token
    * @dev Reverts if the given token ID already exists
    * @param _to address the beneficiary that will own the minted token
    */
   function _mint(address _to, uint256 _id) internal {
       allTokens.push(_id);
       allTokensIndex[_id] = _id;
       super._mint(_to, _id);
   }
  
   function addTokenData(uint _tokenId, string _information, string _URL) public {
           require(ownerOf(_tokenId) == msg.sender);
           tokenData[_tokenId].information = _information;
           tokenData[_tokenId].URL = _URL;

      
   }
  
   function getTokenData(uint _tokenId) public view returns(string Liscence, string URL){
       require(exists(_tokenId));
       Liscence = tokenData[_tokenId].information;
       URL = tokenData[_tokenId].URL;
   }
  
   function() payable{
       require(msg.value > 0.16 ether);
       _mint(msg.sender, tokenIDCount++);
   }
}