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contracts...MyContract4.sol

pragma solidity >=0.7.0 <0.9.0;

contract MyContract {
    
    mapping(address => uint256) public balances;
    address payable wallet;
    
    event Purchase(
        address indexed _buyer,
        uint256 _amount
        );
    
    constructor(address payable _wallet) {
        wallet = _wallet;
    }
    
    fallback() external payable {
        // buyToken();
    }
    
    receive() external payable {
        buyToken();
    }
    
    
    function buyToken() public payable {
        // buy a token
        balances[msg.sender] += 1;
        // send ether to the wallet
        wallet.transfer(msg.value);
        emit Purchase(msg.sender, 1);
        
    }
}