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function checkin() public payable {
    __impl_checkin();
    stop();
}

function __impl_checkin() private {
    address v0;
    uint256 v1;

    v0 = v2;
    *(address*)0x0 = v0;
    *0x20 = 0x0;
    v0 = keccak256(0x0, 0x40);
    v0 = storage[v0];
    if((v0 & 0xFF) != 0x0) {
        revert(0x0, 0x0);
    }

    v0 = v2;
    *(address*)0x0 = v0;
    *0x20 = 0x0;
    v0 = keccak256(0x0, 0x40);
    v1 = storage[v0];
    storage[v0] = (v1 & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00) | 0x1;
}