pragma solidity ^0.4.25;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that revert on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, reverts on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b);

    return c;
  }

  /**
  * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b > 0); // Solidity only automatically asserts 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;
  }

  /**
  * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a);
    uint256 c = a - b;

    return c;
  }

  /**
  * @dev Adds two numbers, reverts on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a);

    return c;
  }

  /**
  * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
  * reverts when dividing by zero.
  */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0);
    return a % b;
  }
}

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);
}

contract UBToken is IERC20{
    
    using SafeMath for uint256;
    
    uint public constant _totalSupply = 0;
    
    string public constant symbol = "UB";
    string public constant name = "UNIFIED BET";
    uint8 public constant decimals = 18;
    
    //1 ether = 1 UB
    uint256 public constant RATE = 1;
    
    address public owner;
    
    mapping (address => uint256) balances;
    mapping (address => mapping(address => uint256)) allowed;
    
    function () payable{
        createToken();
    }
    
    constructor (){
        owner = msg.sender;
        
    }
    
    function createToken() payable {
        require(msg.value > 0);
        
        uint256 tokens = msg.value;
        balances[msg.sender] = balances[msg.sender].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].add(_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];
    }
    
}