pragma solidity ^0.4.11;

pragma solidity ^0.4.11;

interface IERC20 {
    function totalSupply() constant returns (uint256 totalSupply);
    function balanceOf(address _owner) constant returns (uint256 balance);
    function transfer(address _to, uint256 _value) returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);
    function approve(address _spender, uint256 _value) returns (bool success);
    function allowance(address _owner, address _spender) constant returns (uint256 remaining);
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}
pragma solidity ^0.4.11;


/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
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;
  }
}
contract GEM is IERC20 {
    
    using SafeMath for uint256;
    
    uint public _totalSupply = 0;
    
    string public constant symbol = "GEM";
    string public constant name = "GEM";
    uint8 public constant decimals = 18;
    
    uint256 public constant RATE = 3000;
    
    address public owner;
    
    mapping(address => uint256) balances;
    mapping(address => mapping(address =>uint256)) allowed;
    
    function () payable {
        createTokens();
    }
    
   function GEM() {
       owner = msg.sender;
   }
    
    function createTokens() payable {
        require(msg.value > 0);
        
        uint256 tokens = msg.value.mul(RATE);
        balances[msg.sender] = balances [msg.sender].add(tokens);
        _totalSupply = _totalSupply.add(tokens);
        owner.transfer(msg.value);
    }
    
    function totalSupply() constant returns (uint256 totalSupply) {
        return _totalSupply;
    }

    function balanceOf(address _owner) constant returns (uint256 balance) {

        return balances[_owner];
        
    }
    
     function transfer(address _to, uint256 _value) returns (bool success) {
        
        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;
        }
     

    function transferFrom(address _from, address _to, uint256 _value) returns (bool success){
        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;
    }     
              
    function approve(address _spender, uint256 _value) returns (bool success) {
     
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
        
    function allowance(address _owner, address _spender) constant returns (uint256 remaining){
        return allowed [_owner][_spender];
        
    }


    
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}