friend_tech can only buy 1 key in the first transaction?

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 function buyShares ( address sharesSubject, uint256 amount ) public payable {
 uint256 supply = sharesSupply[sharesSubject];
 require (supply > 0 || sharesSubject == msg.sender, "Only the shares' subject can buy the first share" );
 uint256 price = getPrice(supply, amount);
 uint256 protocolFee = price * protocolFeePercent / 1 ether;
 uint256 subjectFee = price * subjectFeePercent / 1 ether;
 require (msg.value >= price + protocolFee + subjectFee, "Insufficient payment" );
 sharesBalance[sharesSubject][msg.sender] = sharesBalance[sharesSubject][msg.sender] + amount;
 sharesSupply[sharesSubject] = supply + amount;
 emit Trade(msg.sender, sharesSubject, true , amount, price, protocolFee, subjectFee, supply + amount);
 (bool success1,) = protocolFeeDestination.call{ value : protocolFee}( "" );
 (bool success2,) = sharesSubject.call{ value : subjectFee}( "" );
 require (success1 && success2, "Unable to send funds" );
 }

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 import {TestHarness} from "../../TestHarness.sol" ;

 interface iFriendtech {
 function buyShares ( address sharesSubject, uint256 amount ) external payable ;
 }

 contract fuck_friend_tech is TestHarness {
 iFriendtech friendtech = iFriendtech( 0xCF205808Ed36593aa40a44F10c7f7C2F67d4A4d4 );

 function setUp ( ) external {
 cheat.createSelectFork( "base" , 4 _119_770);
 cheat.deal(address( this ), 100 ether);
 }

 function test_attack ( ) external {
 friendtech.buyShares{ value : 100 ether}(address( this ), 2 );
 }

 receive() external payable {}
 }

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 function getPrice ( uint256 supply, uint256 amount ) public view returns ( uint256 ) {
 uint256 sum1 = supply == 0 ? 0 : (supply - 1 ) * (supply) * ( 2 * (supply - 1 ) + 1 ) / 6 ;
 uint256 sum2 = supply == 0 && amount == 1
 ? 0
 : (supply - 1 + amount) * (supply + amount) * ( 2 * (supply - 1 + amount) + 1 ) / 6 ;

 uint256 summation = sum2 - sum1;
 return summation * 1 ether / 16 _000;
 }