function enter() {
  
    if (msg.value % 2 != 0 ) {
        msg.sender.send(msg.value);
        return;
    }
	
	uint amount;

	amount = msg.value;


    uint idx = persons.length;
    persons.length += 1;
    persons[idx].etherAddress = msg.sender;
    persons[idx].amount = amount;
 
    

      balance += amount;
  


    while (balance > persons[payoutIdx].amount * 2) {
      uint transactionAmount = persons[payoutIdx].amount * 2;
      persons[payoutIdx].etherAddress.send(transactionAmount);

      balance -= transactionAmount;
      payoutIdx += 1;
    }
  }