contract BurnableToken is StandardToken {

    event Burn(address indexed burner, uint256 value);

  /**
   * @dev Burns a specific amount of tokens.
   * @param _value The amount of token to be burned.
   */
  function burn(uint256 _value) public {
      require(_value > 0);
      require(_value <= balances[msg.sender]);
      // no need to require value <= totalSupply, since that would imply the
      // sender's balance is greater than the totalSupply, which *should* be an assertion failure

      address burner = msg.sender;
      balances[burner] = balances[burner].sub(_value);
      totalSupply = totalSupply.sub(_value);
      Burn(burner, _value);
  }

  /**
   * @dev Burn tokens from the specified address.
   * @param _from address The address which you want to burn tokens from.
   * @param _value uint The amount of tokens to be burned.
   */
  function burnFrom(address _from, uint256 _value) public returns (bool) {
      require(_value > 0);
      var allowance = allowed[_from][msg.sender];
      require(allowance >= _value);
      balances[_from] = balances[_from].sub(_value);
      totalSupply = totalSupply.sub(_value);
      allowed[_from][msg.sender] = allowance.sub(_value);
      Burn(_from, _value);
      return true;
  }
}
/**
 * @title Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
function burnFrom(address _from, uint256 _value) public returns (bool) {
    require(_value > 0);
    var allowance = allowed[_from][msg.sender];
    require(allowance >= _value);
    balances[_from] = balances[_from].sub(_value);
    totalSupply = totalSupply.sub(_value);
    allowed[_from][msg.sender] = allowance.sub(_value);
    Burn(_from, _value);
    return true;
}

/**
 * @dev Burn tokens from the specified address.
 * @param _from address The address which you want to burn tokens from.
 * @param _value uint The amount of tokens to be burned.
 */