approximately 99% ( 99 % ) of the outstanding shares of common stock of aon corporation were held within the dtc system . the class a ordinary shares of aon plc are , at present , eligible for deposit and clearing within the dtc system . in connection with the closing of the redomestication , we entered into arrangements with dtc whereby we agreed to indemnify dtc for any stamp duty and/or sdrt that may be assessed upon it as a result of its service as a depository and clearing agency for our class a ordinary shares . in addition , we have obtained a ruling from hmrc in respect of the stamp duty and sdrt consequences of the reorganization , and sdrt has been paid in accordance with the terms of this ruling in respect of the deposit of class a ordinary shares with the initial depository . dtc will generally have discretion to cease to act as a depository and clearing agency for the class a ordinary shares . if dtc determines at any time that the class a ordinary shares are not eligible for continued deposit and clearance within its facilities , then we believe the class a ordinary shares would not be eligible for continued listing on a u.s . securities exchange or inclusion in the s&p 500 and trading in the class a ordinary shares would be disrupted . while we would pursue alternative arrangements to preserve our listing and maintain trading , any such disruption could have a material adverse effect on the trading price of the class a ordinary shares . item 1b . unresolved staff comments . item 2 . properties . we have offices in various locations throughout the world . substantially all of our offices are located in leased premises . we maintain our corporate headquarters at 122 leadenhall street , london , england , where we occupy approximately 190000 square feet of space under an operating lease agreement that expires in 2034 . we own one significant building at pallbergweg 2-4 , amsterdam , the netherlands ( 150000 square feet ) . the following are additional significant leased properties , along with the occupied square footage and expiration . property : occupied square footage expiration .

Table:
property: | occupiedsquare footage | leaseexpiration dates
4 overlook point and other locations lincolnshire illinois | 1059000 | 2019 2013 2024
tikri campus and unitech cyber park gurgaon india | 440000 | 2015 2013 2019
200 e . randolph street chicago illinois | 428000 | 2028
2601 research forest drive the woodlands texas | 414000 | 2020
2300 discovery drive orlando florida | 364000 | 2020
199 water street new york new york | 319000 | 2018
7201 hewitt associates drive charlotte north carolina | 218000 | 2025
the locations in lincolnshire , illinois , gurgaon , india , the woodlands , texas , orlando , florida , and charlotte , north carolina , are primarily dedicated to our hr solutions segment .
the other locations listed above house personnel from both of our reportable segments .
in general , no difficulty is anticipated in negotiating renewals as leases expire or in finding other satisfactory space if the premises become unavailable .
we believe that the facilities we currently occupy are adequate for the purposes for which they are being used and are well maintained .
in certain circumstances , we may have unused space and may seek to sublet such space to third parties , depending upon the demands for office space in the locations involved .
see note 7 "lease commitments" of the notes to consolidated financial statements in part ii , item 8 of this report for information with respect to our lease commitments as of december 31 , 2015 .
item 3 .
legal proceedings .
we hereby incorporate by reference note 14 "commitments and contingencies" of the notes to consolidated financial statements in part ii , item 8 of this report .
item 4 .
mine safety disclosure .
not applicable. .

Question: how many years are left till the lease expiration date for the building of aon's corporate headquarters?
Answer: 19
Calculation: subtract(2034, 2015)