function flip() public {
        require (A.funded && Z.funded);
        
        Bettor memory winner;
        bool result;
        
        if (block.number % 2 == 0) {
            result = true;
        } else {
            result = false;
        }
        
        if (A.choice == result) {
            winner = A;
        } else {
            winner = Z;
        }
        
        winner.addr.transfer(this.balance);
    }