pragma solidity ^0.4.25;

library SafeMath {
	function mul(uint256 a, uint256 b) internal constant returns (uint256) {
		uint256 c = a * b;
		assert(a == 0 || c / a == b);
		return c;
	}

	function div(uint256 a, uint256 b) internal constant returns (uint256) {
		assert(b > 0); 																			// Solidity automatically throws when dividing by 0
		uint256 c = a / b;
		assert(a == b * c + a % b); 															// There is no case in which this doesn't hold
		return c;
	}

	function sub(uint256 a, uint256 b) internal constant returns (uint256) {
		assert(b <= a);
		return a - b;
	}

	function add(uint256 a, uint256 b) internal constant returns (uint256) {
		uint256 c = a + b;
		assert(c >= a);
		return c;
	}
}

	// ERC20 Token Smart Contract
	contract MARA {	
		string  public constant name 		= "MARA";
		string  public constant symbol 		= "MARA";
		uint8   public constant decimals	= 0;
		uint    public _totalSupply 		= 100000000;
		uint256 public RATE 				= 1;
		bool    public isMinting 			= false;
		string  public constant generatedBy	= "MARAChain Secure Exchange of Digital Documents - www.marachain.eu";
		
		using SafeMath for uint256;
		address public owner;
		
		// Functions with this modifier can only be executed by the owner
		modifier onlyOwner() {
			if (msg.sender != owner) {
				throw;
			}
			_;
		}
		
		mapping(address => uint256) balances;													// Balances for each account
		mapping(address => mapping(address=>uint256)) allowed;									// Owner of account approves the transfer of an amount to another account

		function () payable{																	// Its a payable function works as a token factory
			createTokens();
		}

		// Constructor
		constructor() public {
			owner = 0x65e1A84eFA8f217DA90fDe7a60fA02fDc0cd5b8C; 
			balances[owner] = _totalSupply;
		}

		//allows owner to burn tokens that are not sold in a crowdsale
		function burnTokens(uint256 _value) onlyOwner {
			require(balances[msg.sender] >= _value && _value > 0 );
			_totalSupply = _totalSupply.sub(_value);
			balances[msg.sender] = balances[msg.sender].sub(_value); 
		}

		// This function creates Tokens  
		function createTokens() payable {
			if(isMinting == true){
				require(msg.value > 0);
				uint256  tokens = msg.value.div(100000000000000).mul(RATE);
				balances[msg.sender] = balances[msg.sender].add(tokens);
				_totalSupply = _totalSupply.add(tokens);
				owner.transfer(msg.value);
			}
			else{
				throw;
			}
		}

		function endCrowdsale() onlyOwner {
			isMinting = false;
		}

		function changeCrowdsaleRate(uint256 _value) onlyOwner {
			RATE = _value;
		}
		
		function totalSupply() constant returns(uint256){
			return _totalSupply;
		}
		
		function balanceOf(address _owner) constant returns(uint256){							// What is the balance of a particular account?
			return balances[_owner];
		}
   
		function transfer(address _to, uint256 _value)  returns(bool) {							// Transfer the balance from owner's account to another account
			require(balances[msg.sender] >= _value && _value > 0 );
			balances[msg.sender] = balances[msg.sender].sub(_value);
			balances[_to] = balances[_to].add(_value);
			Transfer(msg.sender, _to, _value);
			return true;
		}
		
	// Send _value amount of tokens from address _from to address _to
	// The transferFrom method is used for a withdraw workflow, allowing contracts to send
	// tokens on your behalf, for example to "deposit" to a contract address and/or to charge
	// fees in sub-currencies; the command should fail unless the _from account has
	// deliberately authorized the sender of the message via some mechanism; we propose
	// these standardized APIs for approval:
	function transferFrom(address _from, address _to, uint256 _value)  returns(bool) {
		require(allowed[_from][msg.sender] >= _value && balances[_from] >= _value && _value > 0);
		balances[_from] = balances[_from].sub(_value);
		balances[_to] = balances[_to].add(_value);
		allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
		Transfer(_from, _to, _value);
		return true;
	}
	
	// Allow _spender to withdraw from your account, multiple times, up to the _value amount.
	// If this function is called again it overwrites the current allowance with _value.
	function approve(address _spender, uint256 _value) returns(bool){
		allowed[msg.sender][_spender] = _value; 
		Approval(msg.sender, _spender, _value);
		return true;
	}
	
	// Returns the amount which _spender is still allowed to withdraw from _owner
	function allowance(address _owner, address _spender) constant returns(uint256){
		return allowed[_owner][_spender];
	}
	
	event Transfer(address indexed _from, address indexed _to, uint256 _value);
	event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}