pragma solidity ^0.4.18;
    
    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;
      }
    }
    
    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]);
    
        // SafeMath.sub will throw if there is not enough balance.
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value);
        return true;
      }
    
      function balanceOf(address _owner) public view returns (uint256 balance) {
        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);
        Transfer(_from, _to, _value);
        return true;
      }
   
      function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
       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);
       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);
        }
       Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
      }
    
    }
    contract TripBitToken is StandardToken {
    
      string public constant name = "TripBit"; // solium-disable-line uppercase
      string public constant symbol = "TBT"; // solium-disable-line uppercase
      uint8 public constant decimals = 18; // solium-disable-line uppercase
      uint256 public constant INITIAL_SUPPLY = 700000000 * (10 ** uint256(decimals));
    
      function TripBitToken() public {
        totalSupply_ = INITIAL_SUPPLY;
        balances[msg.sender] = INITIAL_SUPPLY;
       Transfer(0x0, msg.sender, INITIAL_SUPPLY);
	   }
    }