function () payable public {
        
        uint minimumInvestment = currentInvestment * 11 / 10;
        require(msg.value > minimumInvestment);

        
        address previousInvestor = currentInvestor;
        currentInvestor = msg.sender;
        currentInvestment = msg.value;

        
        
        previousInvestor.send(msg.value);
    }