pragma solidity >=0.4.22 <0.6.0;

  contract Lottery{
address payable[] public  players; //dynamic array with players
addresses
address payable public manager; //contract manager


//contract constructor, runs once at contract deployment
constructor() public{
    //the manager is account address that deploys the contract
    manager = msg.sender;
}

//this fallback payable function will be automatically called when
 somebody
//sends ether to our contract address
function () payable external{
    require(msg.value >= 0.01 ether);
    players.push(msg.sender); //add the address of the account that

                   //sends
                              //ether to players array
}

function get_balance() public view returns(uint){
    require(msg.sender == manager);
    return address(this).balance; //return contract balance
}

//returns a very big pseodo-random integer no.
function random() public view returns(uint256){
     return keccak256(abi.encodePacked(block.difficulty,
  block.timestamp, players.length));<--error is this line

}
function selectWinner() public view returns(address) {
    require(msg.sender == manager);


    uint r = random();

    address payable winner;

    //a random index
    uint index = r % players.length;
    winner = players[index];

    //transfer contract balance to the winner address
    winner.transfer(address(this).balance);

    players = new address payable[](0); //resetting the players
         dynamic array
    }
 }