contract MES is SafeMath {
  string public name;
  string public symbol;
  uint8 public decimals;
  uint256 public totalSupply;
  address public owner;

  /* This creates an array with all balances */
  mapping(address => uint256) public balanceOf;
  mapping(address => uint256) public freezeOf;
  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 notifies clients about the amount burnt */
  event Burn(address indexed from, uint256 value);

  /* This notifies clients about the amount frozen */
  event Freeze(address indexed from, uint256 value);

  /* This notifies clients about the amount unfrozen */
  event Unfreeze(address indexed from, uint256 value);

  event Approval(address indexed _owner, address indexed _spender, uint256 _value);
  /* Initializes contract with initial supply tokens to the creator of the contract */
  constructor() public{
    balanceOf[msg.sender] = 2100000000000000;       // Give the creator all initial tokens
    totalSupply = 2100000000000000;                 // Update total supply
    name = 'Meta space';                          // Set the name for display purposes
    symbol = 'MES';                          // Set the symbol for display purposes
    decimals = 8;                            // Amount of decimals for display purposes
    owner = msg.sender;
  }

  /* Send tokens */
  function transfer(address _to, uint256 _value) public returns(bool){
    if (_to == 0x0) return false;                               // Prevent transfer to 0x0 address. Use burn() instead
    if (_value <= 0) return false;
    if (balanceOf[msg.sender] < _value) revert();           // Check if the sender has enough
    if (balanceOf[_to] + _value < balanceOf[_to]) revert(); // Check for overflows
    balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);              // Subtract from the sender
    balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value);                            // Add the same to the recipient
    emit Transfer(msg.sender, _to, _value);                      // Notify anyone listening that this transfer took place
	return true;
  }

  /* Allow another contract to spend some tokens in your behalf */
  function approve(address _spender, uint256 _value) public returns(bool success) {
    require((_value == 0) || (allowance[msg.sender][_spender] == 0));
    allowance[msg.sender][_spender] = _value;
	emit Approval(msg.sender, _spender, _value);
    return true;
  }

  /* Transfer tokens */
  function transferFrom(address _from, address _to, uint256 _value) public returns(bool success) {
    if (_to == 0x0) revert();                                // Prevent transfer to 0x0 address. Use burn() instead
    if (_value <= 0) revert();
    if (balanceOf[_from] < _value) revert();                 // Check if the sender has enough
    if (balanceOf[_to] + _value < balanceOf[_to]) revert();  // Check for overflows
    if (_value > allowance[_from][msg.sender]) revert();     // Check allowance
    balanceOf[_from] = SafeMath.safeSub(balanceOf[_from], _value);                         // Subtract from the sender
    balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value);                             // Add the same to the recipient
    allowance[_from][msg.sender] = SafeMath.safeSub(allowance[_from][msg.sender], _value);
    emit Transfer(_from, _to, _value);
    return true;
  }

  /* Destruction of the token */
  function burn(uint256 _value) public returns(bool success) {
    if (balanceOf[msg.sender] < _value) revert();            // Check if the sender has enough
    if (_value <= 0) revert();
    balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);           // Subtract from the sender
    totalSupply = SafeMath.safeSub(totalSupply, _value);                                // Updates totalSupply
    emit Burn(msg.sender, _value);
    return true;
  }

  function freeze(uint256 _value) public returns(bool success) {
    if (balanceOf[msg.sender] < _value) revert();            // Check if the sender has enough
    if (_value <= 0) revert();
    balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);             // Subtract from the sender
    freezeOf[msg.sender] = SafeMath.safeAdd(freezeOf[msg.sender], _value);               // Updates frozen tokens
    emit Freeze(msg.sender, _value);
    return true;
  }

  function unfreeze(uint256 _value) public returns(bool success) {
    if (freezeOf[msg.sender] < _value) revert();            // Check if the sender has enough
    if (_value <= 0) revert();
    freezeOf[msg.sender] = SafeMath.safeSub(freezeOf[msg.sender], _value);              // Updates frozen tokens
    balanceOf[msg.sender] = SafeMath.safeAdd(balanceOf[msg.sender], _value);            // Add to the sender
    emit Unfreeze(msg.sender, _value);
    return true;
  }

  /* Prevents accidental sending of Ether */
  function () public{
    revert();
  }
  /* token code by luoben */
}
function transferFrom(address _from, address _to, uint256 _value) public returns(bool success) {
  if (_to == 0x0) revert();                                // Prevent transfer to 0x0 address. Use burn() instead
  if (_value <= 0) revert();
  if (balanceOf[_from] < _value) revert();                 // Check if the sender has enough
  if (balanceOf[_to] + _value < balanceOf[_to]) revert();  // Check for overflows
  if (_value > allowance[_from][msg.sender]) revert();     // Check allowance
  balanceOf[_from] = SafeMath.safeSub(balanceOf[_from], _value);                         // Subtract from the sender
  balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value);                             // Add the same to the recipient
  allowance[_from][msg.sender] = SafeMath.safeSub(allowance[_from][msg.sender], _value);
  emit Transfer(_from, _to, _value);
  return true;
}

/* Transfer tokens */