pragma solidity 0.5.10;
/**
 * @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) {
    uint256 c = a / b;
    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;
  }
}

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  uint256 public totalSupply;
  function balanceOf(address who) external returns (uint256);
  function transfer(address to, uint256 value) external returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;
  mapping(address => uint256) balances;

  /**
  * @dev transfer token for a specified address
  * @param _to The address to transfer to.
  * @param _value The amount to be transferred.
  */
  function transfer(address _to, uint256 _value) external returns (bool) {
    require(_to != address(0));
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

  /**
  * @dev Gets the balance of the specified address.
  * @param _owner The address to query the the balance of.
  * @return An uint256 representing the amount owned by the passed address.
  */
  function balanceOf(address _owner) external returns (uint256 balance) {
    return balances[_owner];
  }
}

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) external returns (uint256);
  function transferFrom(address from, address to, uint256 value) external returns (bool);
  function approve(address spender, uint256 value) external returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) allowed;

  /**
   * @dev Transfer tokens from one address to another
   * @param from address The address which you want to send tokens from
   * @param to address The address which you want to transfer to
   * @param value uint256 the amount of tokens to be transferred
   */
  function transferFrom(address from, address to, uint256 value) external returns (bool) {
    require(to != address(0));

    allowed[from][msg.sender] = allowed[from][msg.sender].sub(value);
    balances[from] = balances[from].sub(value);
    balances[to] = balances[to].add(value);

    emit Transfer(from, to, value);
    return true;
  }

  /**
   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
   *
   * Beware that changing an allowance with this method brings the risk that someone may use both the old
   * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
   * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint256 _value) external returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
   * @dev Function to check the amount of tokens that an owner allowed to a spender.
   * @param _owner address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint256 specifying the amount of tokens still available for the spender.
   */
  function allowance(address _owner, address _spender) external returns (uint256 remaining) {
    return allowed[_owner][_spender];
  }

  function increaseAllowance(address spender, uint256 addedValue) external returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = (allowed[msg.sender][spender].add(addedValue));
    emit Approval(msg.sender, spender, allowed[msg.sender][spender]);
    return true;
  }

  function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = (allowed[msg.sender][spender].sub(subtractedValue));
    emit Approval(msg.sender, spender, allowed[msg.sender][spender]);
    return true;
  }
}

/**
 * @title Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
contract BurnableToken is StandardToken {

    event Burn(address indexed burner, uint256 value);

    /**
     * @dev Burns a specific amount of tokens.
     * @param amount The amount of token to be burned.
     */

    function burn(uint256 amount) external {
        _burn(msg.sender, amount);
    }

    function _burn(address account, uint256 amount) internal {
        require(amount != 0);
        totalSupply = totalSupply.sub(amount);
        balances[account] = balances[account].sub(amount);
        emit Transfer(account, address(0), amount);
    }

    function burnFrom(address account, uint256 amount) external {
        require(amount <= allowed[account][msg.sender]);
        allowed[account][msg.sender] = allowed[account][msg.sender].sub(amount);
        _burn(account, amount);
    }
}

contract CryptoEmporium is BurnableToken {

    string public constant name = "Crypto Emporium";
    string public constant symbol = "EMP";
    uint public constant decimals = 18;
    uint256 public constant initialSupply = 42000000E18;

    constructor () public {
        totalSupply = initialSupply;
        balances[msg.sender] = initialSupply; // Send all tokens to owner
        emit Transfer(address(0), msg.sender, initialSupply);
    }

}