{"pre_text": ["supplementary information on oil and gas producing activities ( unaudited ) 2017 proved reserves decreased by 647 mmboe primarily due to the following : 2022 revisions of previous estimates : increased by 49 mmboe primarily due to the acceleration of higher economic wells in the bakken into the 5-year plan resulting in an increase of 44 mmboe , with the remainder being due to revisions across the business .", "2022 extensions , discoveries , and other additions : increased by 116 mmboe primarily due to an increase of 97 mmboe associated with the expansion of proved areas and wells to sales from unproved categories in oklahoma .", "2022 purchases of reserves in place : increased by 28 mmboe from acquisitions of assets in the northern delaware basin in new mexico .", "2022 production : decreased by 145 mmboe .", "2022 sales of reserves in place : decreased by 695 mmboe including 685 mmboe associated with the sale of our canadian business and 10 mmboe associated with divestitures of certain conventional assets in oklahoma and colorado .", "see item 8 .", "financial statements and supplementary data - note 5 to the consolidated financial statements for information regarding these dispositions .", "2016 proved reserves decreased by 67 mmboe primarily due to the following : 2022 revisions of previous estimates : increased by 63 mmboe primarily due to an increase of 151 mmboe associated with the acceleration of higher economic wells in the u.s .", "resource plays into the 5-year plan and a decrease of 64 mmboe due to u.s .", "technical revisions .", "2022 extensions , discoveries , and other additions : increased by 60 mmboe primarily associated with the expansion of proved areas and new wells to sales from unproven categories in oklahoma .", "2022 purchases of reserves in place : increased by 34 mmboe from acquisition of stack assets in oklahoma .", "2022 production : decreased by 144 mmboe .", "2022 sales of reserves in place : decreased by 84 mmboe associated with the divestitures of certain wyoming and gulf of mexico assets .", "2015 proved reserves decreased by 35 mmboe primarily due to the following : 2022 revisions of previous estimates : decreased by 2 mmboe primarily resulting from an increase of 105 mmboe associated with drilling programs in u.s .", "resource plays and an increase of 67 mmboe in discontinued operations due to technical reevaluation and lower royalty percentages related to lower realized prices , offset by a decrease of 173 mmboe which was largely due to reductions to our capital development program and adherence to the sec 5-year rule .", "2022 extensions , discoveries , and other additions : increased by140 mmboe as a result of drilling programs in our u.s .", "resource plays .", "2022 production : decreased by 157 mmboe .", "2022 sales of reserves in place : u.s .", "conventional assets sales contributed to a decrease of 18 mmboe .", "changes in proved undeveloped reserves as of december 31 , 2017 , 546 mmboe of proved undeveloped reserves were reported , a decrease of 6 mmboe from december 31 , 2016 .", "the following table shows changes in proved undeveloped reserves for 2017 : ( mmboe ) ."], "post_text": ["revisions of prior estimates .", "revisions of prior estimates increased 5 mmboe during 2017 , primarily due to a 44 mmboe increase in the bakken from an acceleration of higher economic wells into the 5-year plan , offset by a decrease of 40 mmboe in oklahoma due to the removal of less economic wells from the 5-year plan .", "extensions , discoveries and other additions .", "increased 57 mmboe through expansion of proved areas in oklahoma. ."], "table": [["beginning of year", "552"], ["revisions of previous estimates", "5"], ["improved recovery", "2014"], ["purchases of reserves in place", "15"], ["extensions discoveries and other additions", "57"], ["dispositions", "2014"], ["transfers to proved developed", "-83 ( 83 )"], ["end of year", "546"]], "table_ori": [["Beginning of year", "552"], ["Revisions of previous estimates", "5"], ["Improved recovery", "—"], ["Purchases of reserves in place", "15"], ["Extensions, discoveries, and other additions", "57"], ["Dispositions", "—"], ["Transfers to proved developed", "(83)"], ["End of year", "546"]]}

Question: what was purchases of reserves in place in 2016?
Evidence:
table_3: beginning of year the purchases of reserves in place of 552 is 15 ;
text_2: 2022 purchases of reserves in place : increased by 28 mmboe from acquisitions of assets in the northern delaware basin in new mexico .
Program: subtract(15, 28)
Answer:
str_answer: -13
exe_answer: -13