interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract owned {
    address public owner;
 

    function owned () public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require (msg.sender == owner);
        _;
    }
 

    function transferOwnership(address newOwner) onlyOwner public {
        if (newOwner != address(0)) {
        owner = newOwner;
      }
    }
}

contract TokenERC20 {
    string public name; 
    string public symbol; 
    uint8 public decimals = 18;  
    uint256 public totalSupply; 

    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
 

    event Transfer(address indexed from, address indexed to, uint256 value);  
    event Burn(address indexed from, uint256 value);
 

    function TokenERC20(uint256 initialSupply, string tokenName, string tokenSymbol) public {
     
        totalSupply = initialSupply * 10 ** uint256(decimals);   
  
        balanceOf[msg.sender] = totalSupply;
        name = tokenName;
        symbol = tokenSymbol;
    }
 
 
 
    function _transfer(address _from, address _to, uint256 _value) internal {
 
   
      require(_to != 0x0);
 
     
      require(balanceOf[_from] >= _value);
 
    
      require(balanceOf[_to] + _value > balanceOf[_to]);
 
     
      uint previousBalances = balanceOf[_from] + balanceOf[_to];
 
   
      balanceOf[_from] -= _value;
 
    
      balanceOf[_to] += _value;
 
     
      Transfer(_from, _to, _value);
 
    
      assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
 
    }
 

    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }
 

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
    
        require(_value <= allowance[_from][msg.sender]);
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }
 

    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }
 

    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;
        }
    }
 

    function burn(uint256 _value) public returns (bool success) {
        
        require(balanceOf[msg.sender] >= _value);
      
        balanceOf[msg.sender] -= _value;
        
        totalSupply -= _value;
        Burn(msg.sender, _value);
        return true;
    }
 

    function burnFrom(address _from, uint256 _value) public returns (bool success) {
       
        require(balanceOf[_from] >= _value);
        
        require(_value <= allowance[_from][msg.sender]);
       
        balanceOf[_from] -= _value;
        allowance[_from][msg.sender] -= _value;
       
        totalSupply -= _value;
        Burn(_from, _value);
        return true;
    }
}
 

contract MyAdvancedToken is owned, TokenERC20 {
 

    uint256 public sellPrice;
 
 
    uint256 public buyPrice;
 

    mapping (address => bool) public frozenAccount;
 

    event FrozenFunds(address target, bool frozen);
 
 

        function MyAdvancedToken(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}
 
 

    function _transfer(address _from, address _to, uint _value) internal {
 
        require (_to != 0x0);
 
       
        require (balanceOf[_from] > _value);
 
        
        require (balanceOf[_to] + _value > balanceOf[_to]);
 
       
        require(!frozenAccount[_from]);
        require(!frozenAccount[_to]);
 
       
        balanceOf[_from] -= _value;
 
     
        balanceOf[_to] += _value;
 
     
        Transfer(_from, _to, _value);
 
    }
 

    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
 
     
        balanceOf[target] += mintedAmount;
        totalSupply += mintedAmount;
 
 
        Transfer(0, this, mintedAmount);
        Transfer(this, target, mintedAmount);
    }
 

    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        FrozenFunds(target, freeze);
    }
 
   
    function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
        sellPrice = newSellPrice;
        buyPrice = newBuyPrice;
    }
 

    function buy() payable public {
      uint amount = msg.value / buyPrice;
 
      _transfer(this, msg.sender, amount);
    }
 

    function sell(uint256 amount) public {
 
      
        require(this.balance >= amount * sellPrice);
 
        _transfer(msg.sender, this, amount);
 
        msg.sender.transfer(amount * sellPrice);
    }
}