function claim() atStage(Stages.Airdrop) {
        require(airdropParticipants < maxAirdropParticipants);

        
        require(now > start);

        
        require(now < start + airdropEnd);

        require(participatedInAirdrop[msg.sender] == false); 

        require(EGREngravedToken.issue(msg.sender, rateAirDrop * 10**3));

        participatedInAirdrop[msg.sender] = true;
        airdropParticipants += 1;
    }