pragma solidity >=0.4.22 <0.6.0;  
  
contract owned {  
    address public owner;  
  
    constructor() 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 calldata _extraData) external; }  
  
contract TokenERC20 {  
    // Public variables of the token  
    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 generates a public event on the blockchain that will notify clients  
    event Approval(address indexed _owner, address indexed _spender, 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 
     */  
    constructor(  
        uint256 initialSupply,  
        string memory tokenName,  
        string memory 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 != address(0x0));  
        // Check if the sender has enough  
        require(balanceOf[_from] >= _value);  
        // Check for overflows  
        require(balanceOf[_to] + _value > balanceOf[_to]);  
        // Save this for an assertion in the future  
        uint previousBalances = balanceOf[_from] + balanceOf[_to];  
        // Subtract from the sender  
        balanceOf[_from] -= _value;  
        // Add the same to the recipient  
        balanceOf[_to] += _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] + 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 returns (bool success) {  
        _transfer(msg.sender, _to, _value);  
        return true;  
    }  
  
    /** 
     * 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] -= _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;  
        emit Approval(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 memory _extraData)  
        public  
        returns (bool success) {  
        tokenRecipient spender = tokenRecipient(_spender);  
        if (approve(_spender, _value)) {  
            spender.receiveApproval(msg.sender, _value, address(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] -= _value;            // Subtract from the sender  
        totalSupply -= _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] -= _value;                         // Subtract from the targeted balance  
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance  
        totalSupply -= _value;                              // Update totalSupply  
        emit Burn(_from, _value);  
        return true;  
    }  
}  
  
/******************************************/  
/*       ADVANCED TOKEN STARTS HERE       */  
/******************************************/  
  
contract Medical is owned, TokenERC20 {  
  
    uint256 public sellPrice;  
    uint256 public buyPrice;  
  
    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 */  
    constructor(  
        uint256 initialSupply,  
        string memory tokenName,  
        string memory 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 != address(0x0));                          // Prevent transfer to 0x0 address. Use burn() instead  
        require (balanceOf[_from] >= _value);                   // Check if the sender has enough  
        require (balanceOf[_to] + _value >= balanceOf[_to]);    // Check for overflows  
        require(!frozenAccount[_from]);                         // Check if sender is frozen  
        require(!frozenAccount[_to]);                           // Check if recipient is frozen  
        balanceOf[_from] -= _value;                             // Subtract from the sender  
        balanceOf[_to] += _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] += mintedAmount;  
        totalSupply += mintedAmount;  
        emit Transfer(address(0), address(this), mintedAmount);  
        emit Transfer(address(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 / buyPrice;                 // calculates the amount  
        _transfer(address(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 {  
        address myAddress = address(this);  
        require(myAddress.balance >= amount * sellPrice);   // checks if the contract has enough ether to buy  
        _transfer(msg.sender, address(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  
    }  
}