pragma solidity ^0.4.13; 
contract owned { 
  address public owner;
  function owned() {
      owner = msg.sender;
  }
  modifier onlyOwner {
      require(msg.sender == owner);
      _;
  }
  function transferOwnership(address newOwner) onlyOwner {
      owner = newOwner;
  }
}
contract tokenRecipient { function receiveApproval(address from, uint256 value, address token, bytes extraData); }
contract token { 
    string public name = 'CTB'; 
    string public symbol; 
    uint8 public decimals; 
    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 token(
      uint256 initialSupply,
      string tokenName,
      uint8 decimalUnits,
      string tokenSymbol
      ) {
      balanceOf[msg.sender] = initialSupply;              
      totalSupply = initialSupply;                        
      name = tokenName;                                   
      symbol = tokenSymbol;                               
      decimals = decimalUnits;                            
  }
  function _transfer(address _from, address _to, uint _value) internal {
      require (_to != 0x0);                               
      require (balanceOf[_from] > _value);                
      require (balanceOf[_to] + _value > balanceOf[_to]); 
      balanceOf[_from] -= _value;                         
      balanceOf[_to] += _value;                            
      Transfer(_from, _to, _value);
  }
  function transfer(address _to, uint256 _value) {
      _transfer(msg.sender, _to, _value);
  }
  function transferFrom(address _from, address _to, uint256 _value) 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)
      returns (bool success) {
      allowance[msg.sender][_spender] = _value;
      return true;
  }
  function approveAndCall(address _spender, uint256 _value, bytes _extraData)
      returns (bool success) {
      tokenRecipient spender = tokenRecipient(_spender);
      if (approve(_spender, _value)) {
          spender.receiveApproval(msg.sender, _value, this, _extraData);
          return true;
      }
  }        
  function burn(uint256 _value) 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) 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 CTB is owned, token {
  uint256 public sellPrice;
  uint256 public buyPrice;
  mapping (address => bool) public frozenAccount;
  event FrozenFunds(address target, bool frozen);
  function CTB(
      uint256 initialSupply,
      string tokenName,
      uint8 decimalUnits,
      string tokenSymbol
  ) token (initialSupply, tokenName, decimalUnits, tokenSymbol) {}
  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 {
      balanceOf[target] += mintedAmount;
      totalSupply += mintedAmount;
      Transfer(0, this, mintedAmount);
      Transfer(this, target, mintedAmount);
  }
  function freezeAccount(address target, bool freeze) onlyOwner {
      frozenAccount[target] = freeze;
      FrozenFunds(target, freeze);
  }
  function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner {
      sellPrice = newSellPrice;
      buyPrice = newBuyPrice;
  }
  function buy() payable {
      uint amount = msg.value / buyPrice;               
      _transfer(this, msg.sender, amount);              
  }
  function sell(uint256 amount) {
      require(this.balance >= amount * sellPrice);      
      _transfer(msg.sender, this, amount);              
      msg.sender.transfer(amount * sellPrice);          
  }
}