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DepositAndRefund.sol

pragma solidity >=0.4.22 <0.6.0;

contract DepositAndRefund {
    
    mapping (address => uint) public balances;
    
    function get_balance(address party) public view returns (uint) {
        return balances[party];
    }
    
    function deposit() public payable returns (uint) {
        balances[msg.sender] += msg.value;
    }
    
    function withdraw(uint amount) public payable {
        require(balances[msg.sender] >= amount);
        balances[msg.sender] -= amount;
        msg.sender.transfer(amount);
    }
}