pragma solidity ^0.4.23;

library SafeMath {

	function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
		if (a == 0) {
      		return 0;
    	}

    	c = a * b;
    	assert(c / a == b);
    	return c;
  	}

	function div(uint256 a, uint256 b) internal pure returns (uint256) {
    	return a / b;
	}

	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 c) {
    	c = a + b;
    	assert(c >= a);
    	return c;
	}
}

contract ERC20Basic {
	function totalSupply() public view returns (uint256);
	function balanceOf(address who) public view returns (uint256);
	function transfer(address to, uint256 value) public returns (bool);
	event Transfer(address indexed from, address indexed to, uint256 value);
}

contract ERC20 is ERC20Basic {
	function allowance(address owner, address spender) public view returns (uint256);
	function transferFrom(address from, address to, uint256 value) public returns (bool);
	function approve(address spender, uint256 value) public returns (bool);
	event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract BasicToken is ERC20Basic {
	using SafeMath for uint256;

	mapping(address => uint256) balances;

	uint256 totalSupply_;

	function totalSupply() public view returns (uint256) {
    	return totalSupply_;
  	}

  	function transfer(address _to, uint256 _value) public returns (bool) {
    	require(_to != address(0));
    	require(_value <= balances[msg.sender]);

    	balances[msg.sender] = balances[msg.sender].sub(_value);
    	balances[_to] = balances[_to].add(_value);
    	emit Transfer(msg.sender, _to, _value);
    	return true;
	}

    function balanceOf(address _owner) public view returns (uint256) {
		return balances[_owner];
	}
	
}

contract StandardToken is ERC20, BasicToken {

	mapping (address => mapping (address => uint256)) internal allowed;

	function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
		require(_to != address(0));
		require(_value <= balances[_from]);
		require(_value <= allowed[_from][msg.sender]);

		balances[_from] = balances[_from].sub(_value);
		balances[_to] = balances[_to].add(_value);
		allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
		emit Transfer(_from, _to, _value);
		return true;
	}

  	function approve(address _spender, uint256 _value) public returns (bool) {
    	allowed[msg.sender][_spender] = _value;
    	emit Approval(msg.sender, _spender, _value);
    	return true;
  	}

  	function allowance(address _owner, address _spender) public view returns (uint256) {
    	return allowed[_owner][_spender];
	}

	function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
    	allowed[msg.sender][_spender] = (allowed[msg.sender][_spender].add(_addedValue));
		emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
		return true;
	}

  	function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
    	uint oldValue = allowed[msg.sender][_spender];
    	if (_subtractedValue > oldValue) {
      		allowed[msg.sender][_spender] = 0;
    	} else {
      		allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    	}
    	emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    	return true;
  	}
}

contract ZionToken is StandardToken {
	
	string public name;
	string public symbol; 
	uint8 public decimals; 

  	constructor (string _name, string _symbol, uint8 _decimals, uint256 _total) public {
		name = _name;
		symbol = _symbol;
		decimals = _decimals;
		totalSupply_ = _total.mul(10 ** uint256(_decimals));
	
    	balances[msg.sender] = totalSupply_;
	
    	emit Transfer(address(0), msg.sender, totalSupply_);
  	}
	
}