pragma solidity 0.4.23;
    
    /**
     * @title SafeMath
     * @dev Math operations with safety checks that throw on error
     */
    library SafeMath {
      function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
          return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
      }
    
      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 c;
      }
    
      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) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
      }
    }
    
    contract owned {
        address public owner;
    	using SafeMath for uint256;
    	
        function owned() public {
            owner = msg.sender;
        }
    
        modifier onlyOwner {
            require(msg.sender == owner);
            _;
        }
    
        function transferOwnership(address newOwner) onlyOwner public {
            owner = newOwner;
        }
    }
    
    interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }
    
    contract TokenERC20 {
        // Public variables of the token
        using SafeMath for uint256;
    	string public name;
        string public symbol;
        uint8 public decimals = 18;
        // 18 decimals is the strongly suggested default, avoid changing it
        uint256 public totalSupply;
    
        // This creates an array with all balances
        mapping (address => uint256) public balanceOf;
        mapping (address => mapping (address => uint256)) public allowance;
    
        // This generates a public event on the blockchain that will notify clients
        event Transfer(address indexed from, address indexed to, uint256 value);
    
        // This notifies clients about the amount burnt
        event Burn(address indexed from, uint256 value);
    
        /**
         * Constrctor function
         *
         * Initializes contract with initial supply tokens to the creator of the contract
         */
        function TokenERC20(
            uint256 initialSupply,
            string tokenName,
            string tokenSymbol
        ) public {
            totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
            balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
            name = tokenName;                                   // Set the name for display purposes
            symbol = tokenSymbol;                               // Set the symbol for display purposes
        }
    
        /**
         * Internal transfer, only can be called by this contract
         */
        function _transfer(address _from, address _to, uint _value) internal {
            // Prevent transfer to 0x0 address. Use burn() instead
            require(_to != 0x0);
            // Check if the sender has enough
            require(balanceOf[_from] >= _value);
            // Check for overflows
            require(balanceOf[_to].add(_value) > balanceOf[_to]);
            // Save this for an assertion in the future
            uint previousBalances = balanceOf[_from].add(balanceOf[_to]);
            // Subtract from the sender
            balanceOf[_from] = balanceOf[_from].sub(_value);
            // Add the same to the recipient
            balanceOf[_to] = balanceOf[_to].add(_value);
            emit Transfer(_from, _to, _value);
            // Asserts are used to use static analysis to find bugs in your code. They should never fail
            assert(balanceOf[_from].add(balanceOf[_to]) == previousBalances);
        }
    
        /**
         * Transfer tokens
         *
         * Send `_value` tokens to `_to` from your account
         *
         * @param _to The address of the recipient
         * @param _value the amount to send
         */
        function transfer(address _to, uint256 _value) public {
            _transfer(msg.sender, _to, _value);
        }
    
        /**
         * Transfer tokens from other address
         *
         * Send `_value` tokens to `_to` in behalf of `_from`
         *
         * @param _from The address of the sender
         * @param _to The address of the recipient
         * @param _value the amount to send
         */
        function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
            require(_value <= allowance[_from][msg.sender]);     // Check allowance
            allowance[_from][msg.sender] = allowance[_from][msg.sender].sub(_value);
            _transfer(_from, _to, _value);
            return true;
        }
    
        /**
         * Set allowance for other address
         *
         * Allows `_spender` to spend no more than `_value` tokens in your behalf
         *
         * @param _spender The address authorized to spend
         * @param _value the max amount they can spend
         */
        function approve(address _spender, uint256 _value) public
            returns (bool success) {
            allowance[msg.sender][_spender] = _value;
            return true;
        }
    
        /**
         * Set allowance for other address and notify
         *
         * Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
         *
         * @param _spender The address authorized to spend
         * @param _value the max amount they can spend
         * @param _extraData some extra information to send to the approved contract
         */
        function approveAndCall(address _spender, uint256 _value, bytes _extraData)
            public
            returns (bool success) {
            tokenRecipient spender = tokenRecipient(_spender);
            if (approve(_spender, _value)) {
                spender.receiveApproval(msg.sender, _value, this, _extraData);
                return true;
            }
        }
    
        /**
         * Destroy tokens
         *
         * Remove `_value` tokens from the system irreversibly
         *
         * @param _value the amount of money to burn
         */
        function burn(uint256 _value) public returns (bool success) {
            require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
            balanceOf[msg.sender] = balanceOf[msg.sender].sub(_value);            // Subtract from the sender
            totalSupply = totalSupply.sub(_value);                      // Updates totalSupply
           emit Burn(msg.sender, _value);
            return true;
        }
    
        /**
         * Destroy tokens from other account
         *
         * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
         *
         * @param _from the address of the sender
         * @param _value the amount of money to burn
         */
        function burnFrom(address _from, uint256 _value) public returns (bool success) {
            require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
            require(_value <= allowance[_from][msg.sender]);    // Check allowance
            balanceOf[_from] = balanceOf[_from].sub(_value);                         // Subtract from the targeted balance
            allowance[_from][msg.sender] = allowance[_from][msg.sender].sub(_value);             // Subtract from the sender's allowance
            totalSupply = totalSupply.sub(_value);                              // Update totalSupply
          emit  Burn(_from, _value);
            return true;
        }
    }
    
    /******************************************/
    /*       ADVANCED TOKEN STARTS HERE       */
    /******************************************/
    
    contract CRYPTOBITECOIN is owned, TokenERC20 {
    
        uint256 public sellPrice;
        uint256 public buyPrice;
    	using SafeMath for uint256;
    	
        mapping (address => bool) public frozenAccount;
    
        /* This generates a public event on the blockchain that will notify clients */
        event FrozenFunds(address target, bool frozen);
    
        /* Initializes contract with initial supply tokens to the creator of the contract */
        function CRYPTOBITECOIN(
            uint256 initialSupply,
            string tokenName,
            string tokenSymbol
        ) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}
    
        /* Internal transfer, only can be called by this contract */
        function _transfer(address _from, address _to, uint _value) internal {
            require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
            require (balanceOf[_from] >= _value);               // Check if the sender has enough
            require (balanceOf[_to].add(_value) >= balanceOf[_to]); // Check for overflows
            require(!frozenAccount[_from]);                     // Check if sender is frozen
            require(!frozenAccount[_to]);                       // Check if recipient is frozen
            balanceOf[_from] = balanceOf[_from].sub(_value);                         // Subtract from the sender
            balanceOf[_to] = balanceOf[_to].add(_value);                           // Add the same to the recipient
           emit Transfer(_from, _to, _value);
        }
		     	
    	
        /// @notice Create `mintedAmount` tokens and send it to `target`
        /// @param target Address to receive the tokens
        /// @param mintedAmount the amount of tokens it will receive
        function mintToken(address target, uint256 mintedAmount) onlyOwner public {
            balanceOf[target] = balanceOf[target].add(mintedAmount);
            totalSupply = totalSupply.add(mintedAmount);
           emit Transfer(0, this, mintedAmount);
           emit Transfer(this, target, mintedAmount);
        }
    
        /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
        /// @param target Address to be frozen
        /// @param freeze either to freeze it or not
        function freezeAccount(address target, bool freeze) onlyOwner public {
            frozenAccount[target] = freeze;
          emit  FrozenFunds(target, freeze);
        }
    
        /// @notice Allow users to buy tokens for `newBuyPrice` eth and sell tokens for `newSellPrice` eth
        /// @param newSellPrice Price the users can sell to the contract
        /// @param newBuyPrice Price users can buy from the contract
        function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
            sellPrice = newSellPrice;
            buyPrice = newBuyPrice;
        }
    
        /// @notice Buy tokens from contract by sending ether
        function buy() payable public {
            uint amount = msg.value.div(buyPrice);               // calculates the amount
            _transfer(this, msg.sender, amount);              // makes the transfers
        }
    
        /// @notice Sell `amount` tokens to contract
        /// @param amount amount of tokens to be sold
        function sell(uint256 amount) public {
            require(this.balance >= amount.mul(sellPrice));      // checks if the contract has enough ether to buy
            _transfer(msg.sender, this, amount);              // makes the transfers
            msg.sender.transfer(amount * sellPrice);          // sends ether to the seller. It's important to do this last to avoid recursion attacks
        }
    }