pragma solidity >=0.5 <0.6;
contract niubInterface{
    string public name;
  string public symbol;
  uint8 public  decimals;
  uint public totalSupply;
    
    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
    function allowance(address _owner, address _spender) public view returns (uint256 remaining);
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

contract niub is niubInterface{
    mapping (address => uint256) private balanceOf;
    mapping (address => mapping (address => uint256)) internal allowed;
    
    constructor() public {
        totalSupply = 100000000000000*1e18; 
        name = "NIUB";
        symbol = "NIUB";
        decimals = 18;
        balanceOf[msg.sender] = totalSupply;
    }


    function transfer(address _to, uint _value) public returns (bool success) {
        require(_to != address(0));
        require(_value <= balanceOf[msg.sender]);
        require(balanceOf[_to] + _value >= balanceOf[_to]);

        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

      function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_to != address(0));
        require(_value <= balanceOf[_from]);
        require(_value <= allowed[_from][msg.sender]);
        require(balanceOf[_to] + _value >= balanceOf[_to]);

        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;

        allowed[_from][msg.sender] -= _value;
        emit Transfer(_from, _to, _value);
        return true;
      }

  function approve(address _spender, uint256 _value) public  returns (bool success) {
          allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
      return allowed[_owner][_spender];
  }
}