function __callback(bytes32 myid, string result, bytes proof) public {
        require(validIds[myid] && msg.sender == oraclize_cbAddress());

        rate = Helpers.parseIntRound(result, 3); 
        delete validIds[myid];
        callbackTime = now;
        waitQuery = false;
        PriceTicker(result, myid, proof);
    }